Tweet
Tweet

Slide 1

Slide 1 text

the RISEof async JavaScript Jeremy Fairbank blog.jeremyfairbank.com @elpapapollo | gh/jfairbank

Slide 2

Slide 2 text

sigient.com

Slide 3

Slide 3 text

No content

Slide 4

Slide 4 text

No content

Slide 5

Slide 5 text

No content

Slide 6

Slide 6 text

No content

Slide 7

Slide 7 text

“Call me maybe?”

Slide 8

Slide 8 text

Async API Callback

Slide 9

Slide 9 text

Callback fetchUserById(1, function(err, user) { if (err) { console.error('Could not retrieve user'); } else { console.log(user); } });

Slide 10

Slide 10 text

}); }); }); }); }); }); Callback Callback Callback Callback Callback Callback

Slide 11

Slide 11 text

function fetchCustomerNameForOrder(orderId, done, fail) { fetchOrder(orderId, function(err, order) { if (err) { logError(err); fail(err); } else { fetchCustomer( order.customerId, function(err, customer) { if (err) { logError(err); fail(err); } else { done(customer.name); } } ); } }); }

Slide 12

Slide 12 text

function fetchCustomerNameForOrder(orderId, done, fail) { fetchOrder(orderId, function(err, order) { if (err) { logError(err); fail(err); } else { fetchCustomer( order.customerId, function(err, customer) { if (err) { logError(err); fail(err); } else { done(customer.name); } } ); } }); }

Slide 13

Slide 13 text

function fetchCustomerNameForOrder(orderId, done, fail) { fetchOrder(orderId, function(err, order) { if (err) { logError(err); fail(err); } else { fetchCustomer( order.customerId, function(err, customer) { if (err) { logError(err); fail(err); } else { done(customer.name); } } ); } }); }

Slide 14

Slide 14 text

Async API ?

Slide 15

Slide 15 text

Promise function fetchCustomerNameForOrder(orderId) { return fetchOrder(orderId) .then(order => fetchCustomer(order.customerId)) .then(customer => customer.name); }

Slide 16

Slide 16 text

.then(...) .then(...) .then(...) .then(...) .then(...) .then(...) .then(...) .then(...)

Slide 17

Slide 17 text

Error Error Error Error

Slide 18

Slide 18 text

function fetchCustomerNameForOrder(orderId) { return fetchOrder(orderId) .then(order => fetchCustomer(order.customerId)) .then(customer => customer.name) .catch(err => { logError(err); throw err; }); }

Slide 19

Slide 19 text

Getting there…

Slide 20

Slide 20 text

• More readable and maintainable • Synchronous-looking but nonblocking • Use native flow control constructs • More declarative and versatile

Slide 21

Slide 21 text

async function fetchCustomerNameForOrder(orderId) { try { const order = await fetchOrder(orderId); const customer = await fetchCustomer(order.customerId); return customer.name; } catch (err) { logError(err); throw err; } }

Slide 22

Slide 22 text

async function fetchCustomerNameForOrder(orderId) { try { const order = await fetchOrder(orderId); const customer = await fetchCustomer(order.customerId); return customer.name; } catch (err) { logError(err); throw err; } }

Slide 23

Slide 23 text

async function fetchCustomerNameForOrder(orderId) { try { const order = await fetchOrder(orderId); const customer = await fetchCustomer(order.customerId); return customer.name; } catch (err) { logError(err); throw err; } }

Slide 24

Slide 24 text

async function fetchCustomerNameForOrder(orderId) { try { const order = await fetchOrder(orderId); const customer = await fetchCustomer(order.customerId); return customer.name; } catch (err) { logError(err); throw err; } }

Slide 25

Slide 25 text

Await

Slide 26

Slide 26 text

function fetchOrder(orderId) { return fetch(`/orders/${orderId}`) .then(response => response.json()); } function printOrder(orderId) { fetchOrder(orderId) .then(order => console.log(order)); }

Slide 27

Slide 27 text

function fetchOrder(orderId) { return fetch(`/orders/${orderId}`) .then(response => response.json()); } async function printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); }

Slide 28

Slide 28 text

async printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); } fetchOrder(orderId) order

Slide 29

Slide 29 text

async printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); } await

Slide 30

Slide 30 text

async printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); } await order

Slide 31

Slide 31 text

await order

Slide 32

Slide 32 text

await order

Slide 33

Slide 33 text

async printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); } ?

Slide 34

Slide 34 text

async function printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); } printOrder(1); Invoke

Slide 35

Slide 35 text

async function printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); } printOrder(1); Encounter await

Slide 36

Slide 36 text

async function printOrder(orderId) { const order = await fetchOrder(orderId); console.log(order); } printOrder(1); Wrap in Promise.resolve

Slide 37

Slide 37 text

Wrap in Promise.resolve async function printOrder(orderId) { const promise = Promise.resolve(fetchOrder(orderId)); console.log(order); } printOrder(1);

Slide 38

Slide 38 text

async function printOrder(orderId) { const promise = Promise.resolve(fetchOrder(orderId)); console.log(order); } printOrder(1); Wrap rest with then callback

Slide 39

Slide 39 text

async function printOrder(orderId) { const promise = Promise.resolve(fetchOrder(orderId)); return promise.then(order => { console.log(order); return Promise.resolve(undefined); }); } printOrder(1); Wrap rest with then callback

Slide 40

Slide 40 text

async function printOrder(orderId) { const promise = Promise.resolve(fetchOrder(orderId)); return promise.then(order => { console.log(order); return Promise.resolve(undefined); }); } printOrder(1); Wrap implicit return with Promise.resolve

Slide 41

Slide 41 text

function fetchCustomerNameForOrder(orderId) { return Promise.resolve(fetchOrder(orderId)) .then(order => { return Promise.resolve(fetchCustomer(order.customerId)) .then(customer => { return Promise.resolve(customer.name); }); }); } ?

Slide 42

Slide 42 text

async function meaningOfLife() { return 42; } meaningOfLife() === 42; ???

Slide 43

Slide 43 text

async function meaningOfLife() { return 42; } function meaningOfLife() { return Promise.resolve(42); } meaningOfLife() .then(answer => answer === 42);

Slide 44

Slide 44 text

Exceptional Situations

Slide 45

Slide 45 text

async function printOrder(orderId) { try { const order = await fetchOrder(orderId); console.log(order); } catch (e) { console.log('Error retrieving order', e); } }

Slide 46

Slide 46 text

async function printOrder(orderId) { try { const order = await fetchOrder(orderId); console.log(order); } catch (e) { console.log('Error retrieving order', e); } } ?

Slide 47

Slide 47 text

function fetchOrder(orderId) { return fetch(`/orders/${orderId}`) .then(resp => { if (resp.status === 404) { throw new Error('Order not found'); } return resp.json(); }); }

Slide 48

Slide 48 text

function fetchOrder(orderId) { return new Promise((resolve, reject) => { $.get(`/orders/${orderId}`) .done(order => resolve(order)) .fail(resp => { if (resp.status === 404) { reject(new Error('Order not found')); } }); }); }

Slide 49

Slide 49 text

Error Error Error Error

Slide 50

Slide 50 text

Regain Control

Slide 51

Slide 51 text

async function findOrCreateOrder(orderId) { let order; if (await orderExists(orderId)) { order = await fetchOrder(orderId); } else { order = await createOrder(); } return order; }

Slide 52

Slide 52 text

async function findOrCreateOrder(orderId) { let order; if (await orderExists(orderId)) { order = await fetchOrder(orderId); } else { order = await createOrder(); } return order; }

Slide 53

Slide 53 text

async function printOrders(orderIds) { for (const id of orderIds) { const order = await fetchOrder(id); console.log(order); } }

Slide 54

Slide 54 text

async function printOrders(orderIds) { for (const id of orderIds) { const order = await fetchOrder(id); console.log(order); } }

Slide 55

Slide 55 text

async function printOrders(orderIds) { for (const id of orderIds) { const order = await fetchOrder(id); console.log(order); } } Problem?

Slide 56

Slide 56 text

async function printOrders(orderIds) { for (const id of orderIds) { const order = await fetchOrder(id); console.log(order); } } printOrders([1, 2, 3]);

Slide 57

Slide 57 text

printOrders([1, 2, 3]); await fetchOrder(1); await fetchOrder(2); await fetchOrder(3);

Slide 58

Slide 58 text

printOrders([1, 2, 3]); await fetchOrder(1); await fetchOrder(2); await fetchOrder(3);

Slide 59

Slide 59 text

printOrders([1, 2, 3]); await fetchOrder(1); await fetchOrder(2); await fetchOrder(3);

Slide 60

Slide 60 text

Order is important

Slide 61

Slide 61 text

async function printOrders(orderIds) { const orders = await Promise.all( orderIds.map(fetchOrder) ); orders.forEach(order => console.log(order)); }

Slide 62

Slide 62 text

async function printOrders(orderIds) { const orders = await Promise.all( orderIds.map(fetchOrder) ); orders.forEach(order => console.log(order)); }

Slide 63

Slide 63 text

printOrders([1, 2, 3]); await Promise.all([ fetchOrder(1), fetchOrder(2), fetchOrder(3) ]);

Slide 64

Slide 64 text

printOrders([1, 2, 3]); Demo rise.of.async.jeremyfairbank.com

Slide 65

Slide 65 text

• Readable, synchronous- like code • Native flow control constructs • Sequential and concurrent processing

Slide 66

Slide 66 text

• Readable, synchronous- like code • Native flow control constructs • Sequential and concurrent processing ✓ ✓ ✓ ✓

Slide 67

Slide 67 text

Events and streams?

Slide 68

Slide 68 text

let counter = 0; function updateCounter(n) { counter += n; counterEl.innerHTML = counter; } incrementBtn.addEventListener('click', () => { updateCounter(1); }); decrementBtn.addEventListener('click', () => { updateCounter(-1); });

Slide 69

Slide 69 text

let counter = 0; function updateCounter(n) { counter += n; counterEl.innerHTML = counter; } incrementBtn.addEventListener('click', () => { updateCounter(1); }); decrementBtn.addEventListener('click', () => { updateCounter(-1); }); ×

Slide 70

Slide 70 text

let counter = 0; async function listenIncrement() { await click(incrementBtn); counter += 1; counterEl.innerHTML = counter; listenIncrement(); }

Slide 71

Slide 71 text

let counter = 0; async function listenIncrement() { await click(incrementBtn); counter += 1; counterEl.innerHTML = counter; listenIncrement(); }

Slide 72

Slide 72 text

let counter = 0; async function listenIncrement() { await click(incrementBtn); counter += 1; counterEl.innerHTML = counter; listenIncrement(); }

Slide 73

Slide 73 text

let counter = 0; async function listenIncrement() { await click(incrementBtn); counter += 1; counterEl.innerHTML = counter; listenIncrement(); }

Slide 74

Slide 74 text

let counter = 0; async function listenIncrement() { await click(incrementBtn); counter += 1; counterEl.innerHTML = counter; listenIncrement(); } ×

Slide 75

Slide 75 text

const source = Observable.merge( Observable.fromEvent(incrementBtn, 'click').mapTo(1), Observable.fromEvent(decrementBtn, 'click').mapTo(-1), ); source .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 76

Slide 76 text

RxJS

Slide 77

Slide 77 text

[ 1, 2, 3, 4, 5 ] Arrays Sequences in space

Slide 78

Slide 78 text

Observables Sequences in time 1 2 3 4 5

Slide 79

Slide 79 text

Reactive

Slide 80

Slide 80 text

Reactive 3

Slide 81

Slide 81 text

const { Observable } = require('rxjs'); const source = Observable.of(1, 2, 3); source.subscribe(x => console.log(x)); // 1 // 2 // 3

Slide 82

Slide 82 text

const { Observable } = require('rxjs'); const source = Observable.of(1, 2, 3); source.subscribe(x => console.log(x)); // 1 // 2 // 3

Slide 83

Slide 83 text

const { Observable } = require('rxjs'); const source = Observable.of(1, 2, 3); source.subscribe(x => console.log(x)); // 1 // 2 // 3

Slide 84

Slide 84 text

const { Observable } = require('rxjs'); const source = Observable.of(1, 2, 3); source.subscribe(x => console.log(x)); // 1 // 2 // 3

Slide 85

Slide 85 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe

Slide 86

Slide 86 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe 1

Slide 87

Slide 87 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe 1

Slide 88

Slide 88 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe

Slide 89

Slide 89 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe 2

Slide 90

Slide 90 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe 2

Slide 91

Slide 91 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe

Slide 92

Slide 92 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe 3

Slide 93

Slide 93 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); console.log subscribe 3

Slide 94

Slide 94 text

Declarative Transformation Operate on events

Slide 95

Slide 95 text

Observable.of(1, 2, 3) .map(n => n * 2) .subscribe(x => console.log(x)); // 2 // 4 // 6

Slide 96

Slide 96 text

Observable.of(1, 2, 3) .map(n => n * 2) .subscribe(x => console.log(x)); // 2 // 4 // 6

Slide 97

Slide 97 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe

Slide 98

Slide 98 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 1

Slide 99

Slide 99 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 1

Slide 100

Slide 100 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 2

Slide 101

Slide 101 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 2

Slide 102

Slide 102 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe

Slide 103

Slide 103 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 2

Slide 104

Slide 104 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 2

Slide 105

Slide 105 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 4

Slide 106

Slide 106 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 4

Slide 107

Slide 107 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe

Slide 108

Slide 108 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 3

Slide 109

Slide 109 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 3

Slide 110

Slide 110 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 6

Slide 111

Slide 111 text

Observable.of(1, 2, 3) console.log n * 2 map subscribe 6

Slide 112

Slide 112 text

Lazy Transformation Do only as much work as needed

Slide 113

Slide 113 text

Observable.range(1, 100) .map(n => n * 2) .filter(n => n > 4) .take(2) .subscribe(x => console.log(x)); // 6 // 8

Slide 114

Slide 114 text

Observable.range(1, 100) .map(n => n * 2) .filter(n => n > 4) .take(2) .subscribe(x => console.log(x)); // 6 // 8

Slide 115

Slide 115 text

Observable.range(1, 100) .map(n => n * 2) .filter(n => n > 4) .take(2) .subscribe(x => console.log(x)); // 6 // 8

Slide 116

Slide 116 text

Observable.range(1, 100) .map(n => n * 2) .filter(n => n > 4) .take(2) .subscribe(x => console.log(x)); // 6 // 8

Slide 117

Slide 117 text

Observable.range(1, 100) .map(n => n * 2) .filter(n => n > 4) .take(2) .subscribe(x => console.log(x)); // 6 // 8

Slide 118

Slide 118 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take

Slide 119

Slide 119 text

console.log n * 2 map subscribe n > 4 1 Observable.range(1, 100) filter 2 take

Slide 120

Slide 120 text

console.log n * 2 map subscribe n > 4 1 Observable.range(1, 100) filter 2 take

Slide 121

Slide 121 text

console.log n * 2 map subscribe n > 4 2 Observable.range(1, 100) filter 2 take

Slide 122

Slide 122 text

console.log n * 2 map subscribe n > 4 2 Observable.range(1, 100) filter 2 take

Slide 123

Slide 123 text

console.log n * 2 map subscribe n > 4 2 Observable.range(1, 100) filter 2 take ×

Slide 124

Slide 124 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take

Slide 125

Slide 125 text

console.log n * 2 map subscribe n > 4 2 Observable.range(1, 100) filter 2 take

Slide 126

Slide 126 text

console.log n * 2 map subscribe n > 4 2 Observable.range(1, 100) filter 2 take

Slide 127

Slide 127 text

console.log n * 2 map subscribe n > 4 4 Observable.range(1, 100) filter 2 take

Slide 128

Slide 128 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take 4

Slide 129

Slide 129 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take 4 ×

Slide 130

Slide 130 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take

Slide 131

Slide 131 text

console.log n * 2 map subscribe n > 4 3 Observable.range(1, 100) filter 2 take

Slide 132

Slide 132 text

console.log n * 2 map subscribe n > 4 3 Observable.range(1, 100) filter 2 take

Slide 133

Slide 133 text

console.log n * 2 map subscribe n > 4 6 Observable.range(1, 100) filter 2 take

Slide 134

Slide 134 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take 6

Slide 135

Slide 135 text

✓ console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take 6

Slide 136

Slide 136 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 2 take 6

Slide 137

Slide 137 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 1 take 6

Slide 138

Slide 138 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 1 take

Slide 139

Slide 139 text

console.log n * 2 map subscribe n > 4 4 Observable.range(1, 100) filter 1 take

Slide 140

Slide 140 text

console.log n * 2 map subscribe n > 4 4 Observable.range(1, 100) filter 1 take

Slide 141

Slide 141 text

console.log n * 2 map subscribe n > 4 8 Observable.range(1, 100) filter 1 take

Slide 142

Slide 142 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 1 take 8

Slide 143

Slide 143 text

✓ console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 1 take 8

Slide 144

Slide 144 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 1 take 8

Slide 145

Slide 145 text

console.log n * 2 map subscribe n > 4 Observable.range(1, 100) filter 0 take 8

Slide 146

Slide 146 text

DOM Events

Slide 147

Slide 147 text

Observable.fromEvent(incrementBtn, 'click') .mapTo(1) .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 148

Slide 148 text

Observable.fromEvent(incrementBtn, 'click') .mapTo(1) .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 149

Slide 149 text

Observable.fromEvent(incrementBtn, 'click') .mapTo(1) .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 150

Slide 150 text

Observable.fromEvent(incrementBtn, 'click') .mapTo(1) .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 151

Slide 151 text

Observable.fromEvent(incrementBtn, 'click') .mapTo(1) .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 152

Slide 152 text

Observable.fromEvent(incrementBtn, 'click') .mapTo(1) .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 153

Slide 153 text

Observable.fromEvent(incrementBtn, 'click') .mapTo(1) .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 154

Slide 154 text

.scan((acc, curr) => acc + curr, 0) Accumulated counter value

Slide 155

Slide 155 text

.scan((acc, curr) => acc + curr, 0) Current event value (1)

Slide 156

Slide 156 text

.scan((acc, curr) => acc + curr, 0) Return new accumulated counter value

Slide 157

Slide 157 text

.scan((acc, curr) => acc + curr, 0) Initial counter value

Slide 158

Slide 158 text

counterEl.innerHTML = counter acc + curr 1 mapTo subscribe 0 scan

Slide 159

Slide 159 text

acc + curr 1 mapTo subscribe e scan 0 counterEl.innerHTML = counter

Slide 160

Slide 160 text

1 mapTo subscribe e scan acc + curr 0 counterEl.innerHTML = counter

Slide 161

Slide 161 text

1 mapTo subscribe 1 scan acc + curr 0 counterEl.innerHTML = counter

Slide 162

Slide 162 text

1 mapTo subscribe scan 1 acc + curr 0 counterEl.innerHTML = counter

Slide 163

Slide 163 text

1 mapTo subscribe scan 1 acc + curr 1 Counter value counterEl.innerHTML = counter

Slide 164

Slide 164 text

1 mapTo subscribe scan 1 acc + curr 1 counterEl.innerHTML = counter

Slide 165

Slide 165 text

acc + curr 1 mapTo subscribe scan 1 counterEl.innerHTML = counter

Slide 166

Slide 166 text

acc + curr 1 mapTo subscribe e scan 1 counterEl.innerHTML = counter

Slide 167

Slide 167 text

1 mapTo subscribe e scan acc + curr 1 counterEl.innerHTML = counter

Slide 168

Slide 168 text

1 mapTo subscribe 1 scan acc + curr 1 counterEl.innerHTML = counter

Slide 169

Slide 169 text

1 mapTo subscribe scan 1 acc + curr 1 counterEl.innerHTML = counter

Slide 170

Slide 170 text

1 mapTo subscribe scan 2 acc + curr 2 Counter value counterEl.innerHTML = counter

Slide 171

Slide 171 text

1 mapTo subscribe scan 2 acc + curr 2 counterEl.innerHTML = counter

Slide 172

Slide 172 text

const source = Observable.merge( Observable.fromEvent(incrementBtn, 'click').mapTo(1), Observable.fromEvent(decrementBtn, 'click').mapTo(-1), ); source .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 173

Slide 173 text

const source = Observable.merge( Observable.fromEvent(incrementBtn, 'click').mapTo(1), Observable.fromEvent(decrementBtn, 'click').mapTo(-1), ); source .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 174

Slide 174 text

const source = Observable.merge( Observable.fromEvent(incrementBtn, 'click').mapTo(1), Observable.fromEvent(decrementBtn, 'click').mapTo(-1), ); source .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 175

Slide 175 text

const source = Observable.merge( Observable.fromEvent(incrementBtn, 'click').mapTo(1), Observable.fromEvent(decrementBtn, 'click').mapTo(-1), ); source .scan((acc, curr) => acc + curr, 0) .subscribe((counter) => { counterEl.innerHTML = counter; });

Slide 176

Slide 176 text

acc + curr 1 mapTo subscribe 0 scan -1 mapTo Increment Decrement counterEl.innerHTML = counter

Slide 177

Slide 177 text

acc + curr 1 mapTo subscribe 0 scan -1 mapTo Increment Decrement e counterEl.innerHTML = counter

Slide 178

Slide 178 text

acc + curr 1 mapTo subscribe 0 scan -1 mapTo Increment Decrement e counterEl.innerHTML = counter

Slide 179

Slide 179 text

acc + curr 1 mapTo subscribe 0 scan -1 mapTo Increment Decrement 1 counterEl.innerHTML = counter

Slide 180

Slide 180 text

acc + curr 1 mapTo subscribe 0 scan -1 mapTo Increment Decrement 1 counterEl.innerHTML = counter

Slide 181

Slide 181 text

acc + curr 1 mapTo subscribe 1 scan -1 mapTo Increment Decrement 1 counterEl.innerHTML = counter

Slide 182

Slide 182 text

acc + curr 1 mapTo subscribe 1 scan -1 mapTo Increment Decrement 1 counterEl.innerHTML = counter

Slide 183

Slide 183 text

acc + curr 1 mapTo subscribe 1 scan -1 mapTo Increment Decrement counterEl.innerHTML = counter

Slide 184

Slide 184 text

acc + curr 1 mapTo subscribe 1 scan -1 mapTo Increment Decrement e counterEl.innerHTML = counter

Slide 185

Slide 185 text

acc + curr 1 mapTo subscribe 1 scan -1 mapTo Increment Decrement e counterEl.innerHTML = counter

Slide 186

Slide 186 text

acc + curr 1 mapTo subscribe 1 scan -1 mapTo Increment Decrement -1 counterEl.innerHTML = counter

Slide 187

Slide 187 text

acc + curr 1 mapTo subscribe 1 scan -1 mapTo Increment Decrement -1 counterEl.innerHTML = counter

Slide 188

Slide 188 text

acc + curr 1 mapTo subscribe 0 scan -1 mapTo Increment Decrement 0 counterEl.innerHTML = counter

Slide 189

Slide 189 text

acc + curr 1 mapTo subscribe 0 scan -1 mapTo Increment Decrement 0 counterEl.innerHTML = counter

Slide 190

Slide 190 text

Async HTTP

Slide 191

Slide 191 text

Promise fetchOrders() .then((orders) => { orders.forEach((order) => { console.log(order); }); });

Slide 192

Slide 192 text

Promise fetchOrders() .then((orders) => { orders.forEach((order) => { console.log(order); }); });

Slide 193

Slide 193 text

Observable fetchOrders() .subscribe((orders) => { orders.forEach((order) => { console.log(order); }); });

Slide 194

Slide 194 text

Why Observables?

Slide 195

Slide 195 text

Promise fetchOrders() .then(orders => orders.filter( order => order.customerName === 'Tucker' )) .then(orders => orders.map(order => order.id)) .then((orderIds) => { orderIds.forEach(id => console.log(id)); });

Slide 196

Slide 196 text

Promise fetchOrders() .then(orders => orders.filter( order => order.customerName === 'Tucker' )) .then(orders => orders.map(order => order.id)) .then((orderIds) => { orderIds.forEach(id => console.log(id)); });

Slide 197

Slide 197 text

Promise fetchOrders() .then(orders => orders.filter( order => order.customerName === 'Tucker' )) .then(orders => orders.map(order => order.id)) .then((orderIds) => { orderIds.forEach(id => console.log(id)); });

Slide 198

Slide 198 text

Promise fetchOrders() .then(orders => orders.filter( order => order.customerName === 'Tucker' )) .then(orders => orders.map(order => order.id)) .then((orderIds) => { orderIds.forEach(id => console.log(id)); });

Slide 199

Slide 199 text

Async async function printCustomerNames() { const orders = await fetchOrders(); const filtered = orders.filter( order => order.customerName === 'Tucker' ); const orderIds = filtered.map(order => order.id); orderIds.forEach(id => console.log(id)); }

Slide 200

Slide 200 text

Async async function printCustomerNames() { const orders = await fetchOrders(); const filtered = orders.filter( order => order.customerName === 'Tucker' ); const orderIds = filtered.map(order => order.id); orderIds.forEach(id => console.log(id)); }

Slide 201

Slide 201 text

Async async function printCustomerNames() { const orders = await fetchOrders(); const filtered = orders.filter( order => order.customerName === 'Tucker' ); const orderIds = filtered.map(order => order.id); orderIds.forEach(id => console.log(id)); }

Slide 202

Slide 202 text

fetchOrders() .mergeAll() .filter( order => order.customerName === 'Tucker' ) .map(order => order.id) .subscribe(id => console.log(id)); Observable

Slide 203

Slide 203 text

fetchOrders() .mergeAll() .filter( order => order.customerName === 'Tucker' ) .map(order => order.id) .subscribe(id => console.log(id)); Observable

Slide 204

Slide 204 text

fetchOrders() .mergeAll() .filter( order => order.customerName === 'Tucker' ) .map(order => order.id) .subscribe(id => console.log(id)); Observable

Slide 205

Slide 205 text

fetchOrders() .mergeAll() .filter( order => order.customerName === 'Tucker' ) .map(order => order.id) .subscribe(id => console.log(id)); Observable

Slide 206

Slide 206 text

fetchOrders() .mergeAll() .filter( order => order.customerName === 'Tucker' ) .map(order => order.id) .subscribe(id => console.log(id)); Observable

Slide 207

Slide 207 text

Cancellation

Slide 208

Slide 208 text

const promise = fetchOrders() .then((orders) => { orders.foreach((order) => { console.log(order); }); }); promise.cancel(); Promise

Slide 209

Slide 209 text

const promise = fetchOrders() .then((orders) => { orders.foreach((order) => { console.log(order); }); }); promise.cancel(); Promise

Slide 210

Slide 210 text

const promise = fetchOrders() .then((orders) => { orders.foreach((order) => { console.log(order); }); }); promise.cancel(); Promise ×

Slide 211

Slide 211 text

Observable const subscription = fetchOrders() .subscribe((orders) => { orders.forEach((order) => { console.log(order); }); }); subscription.unsubscribe();

Slide 212

Slide 212 text

Observable const subscription = fetchOrders() .subscribe((orders) => { orders.forEach((order) => { console.log(order); }); }); subscription.unsubscribe();

Slide 213

Slide 213 text

console.log subscribe fetchOrders() .subscribe(...)

Slide 214

Slide 214 text

console.log subscribe fetchOrders() .subscribe(...)

Slide 215

Slide 215 text

subscription.unsubscribe(); console.log subscribe × fetchOrders() .subscribe(...) ×

Slide 216

Slide 216 text

Create HTTP Requests

Slide 217

Slide 217 text

function fetchOrders() { return Observable.ajax.get('/orders'); } Built-in AJAX

Slide 218

Slide 218 text

function fetchOrders() { return Observable.ajax.get('/orders'); } Built-in AJAX

Slide 219

Slide 219 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Custom Observable Creation

Slide 220

Slide 220 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Custom Observable Creation

Slide 221

Slide 221 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Custom Observable Creation

Slide 222

Slide 222 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Custom Observable Creation

Slide 223

Slide 223 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Custom Observable Creation

Slide 224

Slide 224 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Custom Observable Creation

Slide 225

Slide 225 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Custom Observable Creation ?

Slide 226

Slide 226 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x));

Slide 227

Slide 227 text

Observable.of(1, 2, 3) .subscribe(x => console.log(x)); Subscriber

Slide 228

Slide 228 text

Observable.of(1, 2, 3) .subscribe({ next: x => console.log(x), });

Slide 229

Slide 229 text

Observable.of(1, 2, 3) .subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), }); // 1 // 2 // 3 // Done!

Slide 230

Slide 230 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } fetchOrders().mergeAll().subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), });

Slide 231

Slide 231 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } fetchOrders().mergeAll().subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), });

Slide 232

Slide 232 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } fetchOrders().mergeAll().subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), });

Slide 233

Slide 233 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } fetchOrders().mergeAll() .subscribe(x => console.log(x));

Slide 234

Slide 234 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } fetchOrders().mergeAll() .subscribe(x => console.log(x)); No complete callback

Slide 235

Slide 235 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } fetchOrders().mergeAll() .subscribe(x => console.log(x)); Safe No complete callback

Slide 236

Slide 236 text

const source = Observable.create((subscriber) => { subscriber.next(1); subscriber.error(new Error('Uh oh')); subscriber.next(2); }); source.subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), error: e => console.error(e), }); // 1 // Error: Uh oh

Slide 237

Slide 237 text

const source = Observable.create((subscriber) => { subscriber.next(1); subscriber.error(new Error('Uh oh')); subscriber.next(2); }); source.subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), error: e => console.error(e), }); // 1 // Error: Uh oh

Slide 238

Slide 238 text

const source = Observable.create((subscriber) => { subscriber.next(1); subscriber.error(new Error('Uh oh')); subscriber.next(2); }); source.subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), error: e => console.error(e), }); // 1 // Error: Uh oh

Slide 239

Slide 239 text

const source = Observable.create((subscriber) => { subscriber.next(1); subscriber.error(new Error('Uh oh')); subscriber.next(2); }); source.subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), error: e => console.error(e), }); // 1 // Error: Uh oh Never called

Slide 240

Slide 240 text

Error Handling

Slide 241

Slide 241 text

Error Error Error Error Promises

Slide 242

Slide 242 text

const source = Observable.create((subscriber) => { subscriber.next(1); subscriber.error(new Error('Uh oh')); subscriber.next(2); }); source.subscribe({ next: x => console.log(x), complete: () => console.log('Done!'), error: e => console.error(e), });

Slide 243

Slide 243 text

const source = Observable.create((subscriber) => { subscriber.next(1); subscriber.error(new Error('Uh oh')); subscriber.next(2); }); source.subscribe(x => console.log(x)); ?

Slide 244

Slide 244 text

const source = Observable.create((subscriber) => { subscriber.next(1); subscriber.error(new Error('Uh oh')); subscriber.next(2); }); source.subscribe(x => console.log(x));

Slide 245

Slide 245 text

fetchOrders() .catch((e) => { logError(e); return Observable.of([]); }) .subscribe(x => console.log(x));

Slide 246

Slide 246 text

fetchOrders() .catch((e) => { logError(e); return Observable.of([]); }) .subscribe(x => console.log(x));

Slide 247

Slide 247 text

fetchOrders() .catch((e) => { logError(e); return Observable.of([]); }) .subscribe(x => console.log(x));

Slide 248

Slide 248 text

fetchOrders() .catch((e) => { logError(e); return Observable.of([]); }) .subscribe(x => console.log(x));

Slide 249

Slide 249 text

fetchOrders() .catch((e) => { logError(e); return legacyFetchOrders() .catch((e2) => { logError(e2); return Observable.of([]); }) }) .subscribe(x => console.log(x));

Slide 250

Slide 250 text

fetchOrders() .catch((e) => { logError(e); return legacyFetchOrders() .catch((e2) => { logError(e2); return Observable.of([]); }) }) .subscribe(x => console.log(x));

Slide 251

Slide 251 text

fetchOrders() .catch((e) => { logError(e); return legacyFetchOrders() .catch((e2) => { logError(e2); return Observable.of([]); }) }) .subscribe(x => console.log(x));

Slide 252

Slide 252 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([])

Slide 253

Slide 253 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ✓

Slide 254

Slide 254 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ✓

Slide 255

Slide 255 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([])

Slide 256

Slide 256 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ×

Slide 257

Slide 257 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ×

Slide 258

Slide 258 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ×

Slide 259

Slide 259 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) × ✓

Slide 260

Slide 260 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) × ✓

Slide 261

Slide 261 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([])

Slide 262

Slide 262 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ×

Slide 263

Slide 263 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ×

Slide 264

Slide 264 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) ×

Slide 265

Slide 265 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) × ×

Slide 266

Slide 266 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) × ×

Slide 267

Slide 267 text

console.log catch subscribe legacyFetchOrders() fetchOrders() catch Observable.of([]) × × []

Slide 268

Slide 268 text

Clean Up

Slide 269

Slide 269 text

function fetchOrdersStream() { return Observable.create((subscriber) => { const socket = new WebSocket('ws://example.com'); socket.addEventListener('message', (event) => { subscriber.next(event.data); }); return () => { socket.close(); }; }); }

Slide 270

Slide 270 text

function fetchOrdersStream() { return Observable.create((subscriber) => { const socket = new WebSocket('ws://example.com'); socket.addEventListener('message', (event) => { subscriber.next(event.data); }); return () => { socket.close(); }; }); }

Slide 271

Slide 271 text

function fetchOrdersStream() { return Observable.create((subscriber) => { const socket = new WebSocket('ws://example.com'); socket.addEventListener('message', (event) => { subscriber.next(event.data); }); return () => { socket.close(); }; }); }

Slide 272

Slide 272 text

function fetchOrdersStream() { return Observable.create((subscriber) => { const socket = new WebSocket('ws://example.com'); socket.addEventListener('message', (event) => { subscriber.next(event.data); }); return () => { socket.close(); }; }); } Called when subscription unsubscribes

Slide 273

Slide 273 text

function fetchOrdersStream() { return Observable.create((subscriber) => { const socket = new WebSocket('ws://example.com'); socket.addEventListener('message', (event) => { subscriber.next(event.data); }); return () => { socket.close(); }; }); } Close socket, deallocate resources, etc.

Slide 274

Slide 274 text

Lazy Subscriptions

Slide 275

Slide 275 text

const p1 = fetchOrders(); const p2 = fetchOrders(); const p3 = fetchOrders(); Promises

Slide 276

Slide 276 text

const p1 = fetchOrders(); const p2 = fetchOrders(); const p3 = fetchOrders(); Promises Immediate

Slide 277

Slide 277 text

Observables const o1 = fetchOrders(); const o2 = fetchOrders(); const o3 = fetchOrders(); o1.subscribe(); o2.subscribe(); o3.subscribe();

Slide 278

Slide 278 text

Observables Lazy const o1 = fetchOrders(); const o2 = fetchOrders(); const o3 = fetchOrders(); o1.subscribe(); o2.subscribe(); o3.subscribe();

Slide 279

Slide 279 text

Observables Lazy const o1 = fetchOrders(); const o2 = fetchOrders(); const o3 = fetchOrders(); o1.subscribe(); o2.subscribe(); o3.subscribe(); Issue Request

Slide 280

Slide 280 text

const o1 = fetchOrders(); o1.subscribe(); o1.subscribe(); o1.subscribe();

Slide 281

Slide 281 text

const o1 = fetchOrders(); o1.subscribe(); o1.subscribe(); o1.subscribe(); Pure

Slide 282

Slide 282 text

const o1 = fetchOrders(); o1.subscribe(); o1.subscribe(); o1.subscribe(); Side Effects Pure

Slide 283

Slide 283 text

Hot Cold vs.

Slide 284

Slide 284 text

Observable creates the source Cold

Slide 285

Slide 285 text

Best for one-off unique requests. Cold

Slide 286

Slide 286 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); }

Slide 287

Slide 287 text

function fetchOrders() { return Observable.create((subscriber) => { fetchOrdersFromDb((orders) => { subscriber.next(orders); subscriber.complete(); }); }); } Resource requested/created at subscription time

Slide 288

Slide 288 text

Hot Observable closes over the source

Slide 289

Slide 289 text

Hot Best for multicasting and sharing resources.

Slide 290

Slide 290 text

const socket = new WebSocket('ws://example.com'); const stream = Observable.create((subscriber) => { socket.addEventListener('message', (event) => { subscriber.next(event.data); }); });

Slide 291

Slide 291 text

const socket = new WebSocket('ws://example.com'); const stream = Observable.create((subscriber) => { socket.addEventListener('message', (event) => { subscriber.next(event.data); }); }); Resource created outside subscription

Slide 292

Slide 292 text

const socket = new WebSocket('ws://example.com'); const stream = Observable.create((subscriber) => { socket.addEventListener('message', (event) => { subscriber.next(event.data); }); }); Close over existing resource when subscribing

Slide 293

Slide 293 text

const sub1 = stream.subscribe(x => console.log(x)); const sub2 = stream.subscribe(x => console.log(x));

Slide 294

Slide 294 text

const sub1 = stream.subscribe(x => console.log(x)); const sub2 = stream.subscribe(x => console.log(x)); Shared stream of data

Slide 295

Slide 295 text

fetchOrders() .mergeAll() .filter( order => order.customerName === 'Tucker' ) .map(order => order.id) .subscribe(id => console.log(id)); Recall

Slide 296

Slide 296 text

fetchOrders() .mergeAll() .filter( order => order.customerName === 'Tucker' ) .map(order => order.id) .subscribe(id => console.log(id)); ? Recall

Slide 297

Slide 297 text

Observable.of([1, 2, 3]) .subscribe(x => console.log(x)); // [ 1, 2, 3 ]

Slide 298

Slide 298 text

Observable.of([1, 2, 3]) .subscribe(x => console.log(x)); // [ 1, 2, 3 ]

Slide 299

Slide 299 text

Observable.of([1, 2, 3]) .subscribe(x => console.log(x)); // [ 1, 2, 3 ]

Slide 300

Slide 300 text

Observable.of([1, 2, 3]) .mergeAll() .subscribe(x => console.log(x)); // 1 // 2 // 3

Slide 301

Slide 301 text

Observable.of([1, 2, 3]) .mergeAll() .subscribe(x => console.log(x)); // 1 // 2 // 3 Flatten

Slide 302

Slide 302 text

Observable.of([1, 2, 3]) .mergeAll() .subscribe(x => console.log(x)); // 1 // 2 // 3

Slide 303

Slide 303 text

subscribe mergeAll console.log [1, 2, 3]

Slide 304

Slide 304 text

subscribe mergeAll console.log [1, 2, 3]

Slide 305

Slide 305 text

subscribe mergeAll console.log [2, 3] 1

Slide 306

Slide 306 text

subscribe mergeAll console.log [2, 3] 1

Slide 307

Slide 307 text

subscribe mergeAll console.log [3] 2

Slide 308

Slide 308 text

subscribe mergeAll console.log [3] 2

Slide 309

Slide 309 text

subscribe mergeAll console.log 3

Slide 310

Slide 310 text

subscribe mergeAll console.log 3

Slide 311

Slide 311 text

Higher Order Observables

Slide 312

Slide 312 text

Observable.of(1, 2, 3) .map(n => n * 2) .subscribe(x => console.log(x)); // 2 // 4 // 6

Slide 313

Slide 313 text

Observable.of(1, 2, 3) .map(n => n * 2) .subscribe(x => console.log(x)); // 2 // 4 // 6 Delay?

Slide 314

Slide 314 text

Observable.of(1, 2, 3) .map(n => Observable.of(n * 2)) .subscribe(x => console.log(x)); // ScalarObservable { value: 2 } // ScalarObservable { value: 4 } // ScalarObservable { value: 6 }

Slide 315

Slide 315 text

Observable.of(1, 2, 3) .map(n => Observable.of(n * 2)) .subscribe(x => console.log(x)); // ScalarObservable { value: 2 } // ScalarObservable { value: 4 } // ScalarObservable { value: 6 }

Slide 316

Slide 316 text

Observable.of(1, 2, 3) .map(n => Observable.of(n * 2)) .subscribe(x => console.log(x)); // ScalarObservable { value: 2 } // ScalarObservable { value: 4 } // ScalarObservable { value: 6 }

Slide 317

Slide 317 text

Observable.of(1, 2, 3) .map(n => Observable.of(n * 2)) .mergeAll() .subscribe(x => console.log(x)); // 2 // 4 // 6

Slide 318

Slide 318 text

Observable.of(1, 2, 3) .map(n => Observable.of(n * 2)) .mergeAll() .subscribe(x => console.log(x)); // 2 // 4 // 6

Slide 319

Slide 319 text

Observable.of(1, 2, 3) .mergeMap(n => Observable.of(n * 2)) .subscribe(x => console.log(x)); // 2 // 4 // 6

Slide 320

Slide 320 text

subscribe mergeMap console.log Observable.of(n * 2)

Slide 321

Slide 321 text

subscribe mergeMap console.log Observable.of(n * 2) 1

Slide 322

Slide 322 text

subscribe mergeMap console.log Observable.of(n * 2) 1

Slide 323

Slide 323 text

subscribe mergeMap console.log Observable.of(n * 2) Observable.of(2) subscribe 2

Slide 324

Slide 324 text

subscribe mergeMap console.log Observable.of(n * 2) Observable.of(2) subscribe 2

Slide 325

Slide 325 text

subscribe mergeMap console.log Observable.of(n * 2) Observable.of(2) subscribe 2

Slide 326

Slide 326 text

Observable.of(1) .delay(1000) .subscribe(x => console.log(x)) // // 1

Slide 327

Slide 327 text

Observable.of(1) .delay(1000) .subscribe(x => console.log(x)) // // 1

Slide 328

Slide 328 text

Observable.of(1) .delay(1000) .subscribe(x => console.log(x)) // // 1

Slide 329

Slide 329 text

Observable.of(1) .delay(1000) .subscribe(x => console.log(x)) // // 1

Slide 330

Slide 330 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) )) .subscribe(x => console.log(x)); // // 2 // 4 // 6

Slide 331

Slide 331 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) )) .subscribe(x => console.log(x)); // // 2 // 4 // 6

Slide 332

Slide 332 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) )) .subscribe(x => console.log(x)); // // 2 // 4 // 6

Slide 333

Slide 333 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) )) .subscribe(x => console.log(x)); // // 2 // 4 // 6 ?

Slide 334

Slide 334 text

Concurrency

Slide 335

Slide 335 text

subscribe mergeMap console.log Observable.of(n * 2)

Slide 336

Slide 336 text

subscribe mergeMap console.log Observable.of(n * 2) 1

Slide 337

Slide 337 text

subscribe mergeMap console.log Observable.of(n * 2) 1

Slide 338

Slide 338 text

subscribe mergeMap console.log Observable.of(n * 2) 2

Slide 339

Slide 339 text

subscribe mergeMap console.log Observable.of(n * 2) 2 2

Slide 340

Slide 340 text

subscribe mergeMap console.log Observable.of(n * 2) 2 2

Slide 341

Slide 341 text

subscribe mergeMap console.log Observable.of(n * 2) 2 4

Slide 342

Slide 342 text

subscribe mergeMap console.log Observable.of(n * 2) 3 2 4

Slide 343

Slide 343 text

subscribe mergeMap console.log Observable.of(n * 2) 3 2 4

Slide 344

Slide 344 text

subscribe mergeMap console.log Observable.of(n * 2) 2 4 6

Slide 345

Slide 345 text

subscribe mergeMap console.log Observable.of(n * 2) 2 4 6

Slide 346

Slide 346 text

subscribe mergeMap console.log Observable.of(n * 2) 4 6 2

Slide 347

Slide 347 text

subscribe mergeMap console.log Observable.of(n * 2) 6 4

Slide 348

Slide 348 text

subscribe mergeMap console.log Observable.of(n * 2) 6

Slide 349

Slide 349 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) ), 1) .subscribe(x => console.log(x)); // // 2 // // 4 // // 6

Slide 350

Slide 350 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) ), 1) .subscribe(x => console.log(x)); // // 2 // // 4 // // 6

Slide 351

Slide 351 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) ), 1) .subscribe(x => console.log(x)); // // 2 // // 4 // // 6

Slide 352

Slide 352 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) ), 1) .subscribe(x => console.log(x)); // // 2 // // 4 // // 6

Slide 353

Slide 353 text

Observable.of(1, 2, 3) .mergeMap(n => ( Observable.of(n * 2).delay(1000) ), 1) .subscribe(x => console.log(x)); // // 2 // // 4 // // 6

Slide 354

Slide 354 text

Observable.of(1, 2, 3) .concatMap(n => ( Observable.of(n * 2).delay(1000) )) .subscribe(x => console.log(x)); // // 2 // // 4 // // 6

Slide 355

Slide 355 text

subscribe concatMap console.log Observable.of(n * 2)

Slide 356

Slide 356 text

subscribe console.log Observable.of(n * 2) 1 concatMap

Slide 357

Slide 357 text

subscribe console.log Observable.of(n * 2) 1 concatMap

Slide 358

Slide 358 text

subscribe console.log Observable.of(n * 2) 2 concatMap

Slide 359

Slide 359 text

subscribe console.log Observable.of(n * 2) 2 concatMap

Slide 360

Slide 360 text

subscribe console.log Observable.of(n * 2) 2 concatMap

Slide 361

Slide 361 text

subscribe console.log Observable.of(n * 2) 2 concatMap

Slide 362

Slide 362 text

subscribe console.log Observable.of(n * 2) 2 concatMap

Slide 363

Slide 363 text

subscribe console.log Observable.of(n * 2) 4 concatMap

Slide 364

Slide 364 text

subscribe console.log Observable.of(n * 2) 4 concatMap

Slide 365

Slide 365 text

subscribe console.log Observable.of(n * 2) 4 concatMap

Slide 366

Slide 366 text

subscribe console.log Observable.of(n * 2) 3 concatMap

Slide 367

Slide 367 text

subscribe console.log Observable.of(n * 2) 3 concatMap

Slide 368

Slide 368 text

subscribe console.log Observable.of(n * 2) 6 concatMap

Slide 369

Slide 369 text

subscribe console.log Observable.of(n * 2) 6 concatMap

Slide 370

Slide 370 text

subscribe console.log Observable.of(n * 2) 6 concatMap

Slide 371

Slide 371 text

Rate Limiting

Slide 372

Slide 372 text

Observable.of(1, 2, 3) .concatMap((id) => { const url = `/orders/${id}`; return Observable.ajax.get(url) .delay(1000); }) .pluck('response') .bufferCount(3) .subscribe(x => console.log(x)); // [ { id: '1', name: 'Order 1' }, // { id: '2', name: 'Order 2' }, // { id: '3', name: 'Order 3' } ]

Slide 373

Slide 373 text

Observable.of(1, 2, 3) .concatMap((id) => { const url = `/orders/${id}`; return Observable.ajax.get(url) .delay(1000); }) .pluck('response') .bufferCount(3) .subscribe(x => console.log(x)); // [ { id: '1', name: 'Order 1' }, // { id: '2', name: 'Order 2' }, // { id: '3', name: 'Order 3' } ]

Slide 374

Slide 374 text

Observable.of(1, 2, 3) .concatMap((id) => { const url = `/orders/${id}`; return Observable.ajax.get(url) .delay(1000); }) .pluck('response') .bufferCount(3) .subscribe(x => console.log(x)); // [ { id: '1', name: 'Order 1' }, // { id: '2', name: 'Order 2' }, // { id: '3', name: 'Order 3' } ]

Slide 375

Slide 375 text

Observable.of(1, 2, 3) .concatMap((id) => { const url = `/orders/${id}`; return Observable.ajax.get(url) .delay(1000); }) .pluck('response') .bufferCount(3) .subscribe(x => console.log(x)); // [ { id: '1', name: 'Order 1' }, // { id: '2', name: 'Order 2' }, // { id: '3', name: 'Order 3' } ]

Slide 376

Slide 376 text

Observable .ajax .get(url) subscribe console.log pluck bufferCount 'response' 3 concatMap

Slide 377

Slide 377 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 3 1

Slide 378

Slide 378 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 3

Slide 379

Slide 379 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 3 R Rate limit next request

Slide 380

Slide 380 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 3 R

Slide 381

Slide 381 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 3 R

Slide 382

Slide 382 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 3 O1

Slide 383

Slide 383 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 2 O1

Slide 384

Slide 384 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 2 O1 +

Slide 385

Slide 385 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 1 O1 O2

Slide 386

Slide 386 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 1 O1 O2 +

Slide 387

Slide 387 text

Observable .ajax .get(url) subscribe concatMap console.log pluck bufferCount 'response' 0 O1 O2 O3

Slide 388

Slide 388 text

Observable .ajax .get(url) subscribe concatMap console.log […] pluck bufferCount 'response' 0

Slide 389

Slide 389 text

Sequential vs. Parallel

Slide 390

Slide 390 text

const promise = Promise.all([ fetchOrder(1), fetchOrder(2), fetchOrder(3), ]); promise.then(x => console.log(x)); // [ { id: '1', name: 'Order 1' }, // { id: '2', name: 'Order 2' }, // { id: '3', name: 'Order 3' } ]

Slide 391

Slide 391 text

const promise = Promise.all([ fetchOrder(1), fetchOrder(2), fetchOrder(3), ]); promise.then(x => console.log(x)); // [ { id: '1', name: 'Order 1' }, // { id: '2', name: 'Order 2' }, // { id: '3', name: 'Order 3' } ]

Slide 392

Slide 392 text

const source = Observable.forkJoin( fetchOrder(1), fetchOrder(2), fetchOrder(3) ); source.subscribe(x => console.log(x)); // [ { response: { id: 1, name: 'Order 1' } }, // { response: { id: 2, name: 'Order 2' } }, // { response: { id: 3, name: 'Order 3' } } ]

Slide 393

Slide 393 text

const source = Observable.forkJoin( fetchOrder(1), fetchOrder(2), fetchOrder(3) ); source.subscribe(x => console.log(x)); // [ { response: { id: 1, name: 'Order 1' } }, // { response: { id: 2, name: 'Order 2' } }, // { response: { id: 3, name: 'Order 3' } } ]

Slide 394

Slide 394 text

const source = Observable.forkJoin( fetchOrder(1), fetchOrder(2), fetchOrder(3) ); source.subscribe(x => console.log(x)); // [ { response: { id: 1, name: 'Order 1' } }, // { response: { id: 2, name: 'Order 2' } }, // { response: { id: 3, name: 'Order 3' } } ] Observable or Promise

Slide 395

Slide 395 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin subscribe console.log

Slide 396

Slide 396 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin subscribe console.log R1

Slide 397

Slide 397 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin R1 subscribe console.log

Slide 398

Slide 398 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin R1 subscribe console.log R3

Slide 399

Slide 399 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin R1 R3 subscribe console.log

Slide 400

Slide 400 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin R1 R3 subscribe console.log R2

Slide 401

Slide 401 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin R1 R2 R3 subscribe console.log

Slide 402

Slide 402 text

fetchOrder(1) fetchOrder(2) fetchOrder(3) forkJoin subscribe console.log R1 R2 R3

Slide 403

Slide 403 text

• Declarative, lazy operations • Expressive event management • No more error swallowing • Rate limiting and concurrent processing

Slide 404

Slide 404 text

• Declarative, lazy operations • Expressive event management • No more error swallowing • Rate limiting and concurrent processing ✓ ✓ ✓ ✓

Slide 405

Slide 405 text

Resources

Slide 406

Slide 406 text

Browser compatibility:
 kangax.github.io/compat-table/es2016plus Node compatibility:
 node.green Async

Slide 407

Slide 407 text

Async babeljs.io

Slide 408

Slide 408 text

Observables github.com/ReactiveX/rxjs RxJS

Slide 409

Slide 409 text

Observables ECMAScript Proposal:
 github.com/tc39/proposal-observable Another spec implementation:
 github.com/zenparsing/zen-observable

Slide 410

Slide 410 text

THANKS! Jeremy Fairbank blog.jeremyfairbank.com @elpapapollo | gh/jfairbank bit.ly/devnexus-rise-of-async SLIDES: github.com/jfairbank/rise-of-async-js-talk CODE: