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Back to the future of JS
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Willian Martins
July 03, 2018
Technology
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Back to the future of JS
This is an extended version of my talk I gave @ NodeJs Meetup in Berlin in July 2018
Willian Martins
July 03, 2018
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Transcript
Hallo!
https://github.com/tc39/proposals
NodeJs Meetup
@wmsbill What is this?
@wmsbill this in the global scope Browser - window Web
worker - self NodeJS - module.exports
@wmsbill this inside a function?
@wmsbill this inside a function?
None
@wmsbill How to make this predictable? Reasoning the value of
this is tricky Function.prototype.bind Arrow function () => {}
With .bind()
With Arrow
@wmsbill Calling a knowing function
@wmsbill Extracting a method from an object
None
@wmsbill Two syntaxes Unary : :context.method() Binary context: :method()
@wmsbill Binary syntax
@wmsbill Unary syntax
@wmsbill
@wmsbill
@wmsbill
@wmsbill Bind operator is good for virtual methods But relies
on this to be bound
@wmsbill Composing without this
@wmsbill
@wmsbill
None
@wmsbill Pipeline operator |> It is a syntax sugar for
function composition It creates a way to streamline a chain of functions
@wmsbill Pipeline operator |>
@wmsbill
@wmsbill
@wmsbill
@wmsbill Function with more params
@wmsbill Function with more params
@wmsbill Awaiting a function
@wmsbill Awaiting a function
@wmsbill Awaiting a function
@wmsbill Awaiting a function
@wmsbill Awaiting a function
None
@wmsbill Smart pipeline
@wmsbill Smart pipeline Two types bare style and topic style
() or [] are disallowed in bare style When () or [] is needed, topic style is used # token is subject to change
@wmsbill What about curry?
None
@wmsbill F# pipeline proposal Extends the minimal proposal with an
await step Await step waits for the resolution of the previous step
@wmsbill F# pipeline proposal
@wmsbill
@wmsbill Partial application f(…) arity = n; partialapp(f(…)) arity =
m; m < n
@wmsbill
@wmsbill
@wmsbill Partial application in ES Achievable by Function.prototype.bind .bind() binds
context and parameters
@wmsbill
@wmsbill What about currying? We can achieve partial application with
curry Curry ≠ Partial application Curry returns arity n-1
@wmsbill
@wmsbill Partial application with arrow function
None
@wmsbill Partial application proposal Creates two new parameters tokens ?
For single argument . . . for multiple parameters
@wmsbill Partial application syntax
@wmsbill With arbitrary parameter
None
@wmsbill The . . . token Spread the unbound parameters
Useful when you want to bound first or last parameter
@wmsbill The . . . token
@wmsbill The . . . token
None
@wmsbill Partial application + pipeline
@wmsbill Partial application + pipeline
@wmsbill Should I use all of it in production? These
proposal are in very early stage The adoption of one, may change the syntax/semantics of other Not production ready (yet)
@wmsbill Let’s talk about something more solid?
None
@wmsbill [].flatMap syntax
@wmsbill [].flatMap syntax
[].flatMap x [].map
@wmsbill [].flatMap x [].map [].map guarantees the same array size
based on input [].flatMap doesn’t guarantees same array length as input array It could be used as filtering
@wmsbill [].flatMap as filter
@wmsbill #smooshgate
@wmsbill [].flatten
@wmsbill [].flatten syntax
@wmsbill [].flatten syntax
@wmsbill [].flatten syntax
@wmsbill So what is the deal?
MooTools
@wmsbill #smooshgate MooTools is an 11 years old ancient lib
They implemented [].flatten with different behavior The implementation + Elements Enhanced HTML component breaks the compatibility w/ [].flatten
https://youtu.be/loqVnZywmvw
@wmsbill TC39 had two options Change flatten to another name
(like smoosh) Break the internet
Array.prototype.flatten
Array.prototype.flatten
https://medium.com/@wmsbill https://twitter.com/wmsbill wmsbill@gmail.com
Dankeshön!