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@adunkman
Executing JavaScript
Across Browser Contexts
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@adunkman
Standard Browser
APIs
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@adunkman
Between Tabs
Outside Tabs
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@adunkman
donate.splcenter.org
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@adunkman
rest in peace,
vine.
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@adunkman
Standard Browser
APIs
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@adunkman
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@adunkman
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@adunkman
Cache-Control
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@adunkman
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@adunkman
There’s more to the
web than web pages
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@adunkman
Browser Contexts
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@adunkman
Window Sandbox
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@adunkman
Domain-Level Objects
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@adunkman
Why isn’t this better?
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@adunkman
document.cookie
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Bob Dunkman c. 1977
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Bob Dunkman c. 2016
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@adunkman
document.cookie
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In document.cookie =
cookieName + "=" +
encodeURIComponent(json);
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In
Out
document.cookie =
cookieName + "=" +
encodeURIComponent(json);
var regex = new RegExp(
"(?:(?:^|.*;)\\s*" + n +
"\\s*\\=\\s*([^;]*).*$)|^.*$");
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In
Out
Detect
document.cookie =
cookieName + "=" +
encodeURIComponent(json);
var regex = new RegExp(
"(?:(?:^|.*;)\\s*" + n +
"\\s*\\=\\s*([^;]*).*$)|^.*$");
setInterval(checkForChanges,
pollingInterval);
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@adunkman
Please don’t.
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@adunkman
document.cookie
localStorage
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@adunkman
QuotaExceededError
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@adunkman
document.cookie
localStorage
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In localStorage.setItem(
keyName, json);
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In
Out
localStorage.setItem(
keyName, json);
localStorage.getItem(
keyName);
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In
Out
Detect
localStorage.setItem(
keyName, json);
localStorage.getItem(
keyName);
window.addEventListener(
“storage", function (event)
{ ...
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var tabId = Math.random();
video.addEventListener("play",
function () {
localStorage.setItem("playing_tab", tabId);
});
window.addEventListener("storage",
function (event) {
var isThisKey = event.key === "playing_tab";
var notThisTab = event.newValue !== tabId;
if (isThisKey && notThisTab) {
video.pause();
}
});
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var tabId = Math.random();
video.addEventListener("play", function () {
localStorage.setItem("playing_tab", tabId);
});
window.addEventListener("storage", function (event) {
if (event.key === "playing_tab" && event.newValue !== tabId) {
video.pause();
}
});
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var tabId = Math.random();
video.addEventListener("play", function () {
localStorage.setItem("playing_tab", tabId);
});
window.addEventListener("storage", function (event) {
if (event.key === "playing_tab" && event.newValue !== tabId) {
video.pause();
}
});
9
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@adunkman
Between Tabs
Outside Tabs
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@adunkman
WebWorker
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@adunkman
SharedWorker
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@adunkman
Tab 1 Tab 2 Tab 3
worker.js 1 worker.js 2 worker.js 3
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@adunkman
Tab 1 Tab 2 Tab 3
worker.js 1
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%
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External Page
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External Page Harvest Script
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External Page Harvest Script
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External Page Harvest Script
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External Page Harvest Script
SharedWorker
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External Page Harvest Script
SharedWorker
WebSocket
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@adunkman
SharedWorker
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@adunkman
Great for sharing
processing and
resources
Not great for
working in Safari
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@adunkman
SharedWorker
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@adunkman
ServiceWorker
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@adunkman
Service workers essentially act as proxy
servers that sit between web applications, and
the browser and network (when available).
… They will also allow access to push
notifications and background sync APIs.
–MDN
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@adunkman
Service workers essentially act as proxy
servers that sit between web applications, and
the browser and network (when available).
… They will also allow access to push
notifications and background sync APIs.
–MDN
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@adunkman
A service worker is an event-
driven worker registered
against an origin and a path.
–MDN
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@adunkman
A service worker is an event-
driven worker registered
against an origin and a path.
–MDN
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@adunkman
Service workers are a new
browser feature that provide
event-driven scripts that run
independently of web pages.
–W3C
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@adunkman
Service workers are a new
browser feature that provide
event-driven scripts that run
independently of web pages.
–W3C
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@adunkman
A service worker is a process
which is tied to domain events
rather than to a browsing context.
–me
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@adunkman
Tab 1
worker.js 1
Domain Events
worker.js 1
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@adunkman
Domain Events
worker.js 1
push
sync
fetch
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@adunkman
“push” event
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@adunkman
Notification Service
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
Tab 1
worker.js 1
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
Tab 1
worker.js 1
(new version)
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
Tab 1
worker.js 1
Tab 2
(new version)
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
Tab 1
worker.js 1
Tab 2
(old) worker.js 1
(new version)
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
Tab 2
(new) worker.js 1
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Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
Worker self.addEventListener("install",
function (event) {
self.skipWaiting();
});
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Worker
Page navigator.serviceWorker.register("sw.js")
.then(function (reg) {
console.log("success", reg);
}).catch(function (err) {
console.log("fail", err);
});
self.addEventListener("push",
function (event) {
console.log("message", event);
});
self.addEventListener("install",
function (event) {
self.skipWaiting();
});
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@adunkman
“push” event
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@adunkman
Browser message
server (like native app)
Wakes ServiceWorker
to process event
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@adunkman
“sync” event
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Worker
Page navigator.serviceWorker.ready
.then(function (reg) {
return reg.sync.register("syncTime");
});
self.addEventListener("sync",
function (event) {
if (event.tag === "syncTime") {
event.waitUntil(stuff());
}
});
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Tab 1
worker.js 1
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Tab 1
worker.js 1
sync “syncTime”
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Tab 1
worker.js 1
sync “syncTime” Browser
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worker.js 1
Browser
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worker.js 1
Browser
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@adunkman
“sync” event
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@adunkman
Great for
backgrounding a sync
process, even in limited
or no connectivity
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@adunkman
“fetch” event
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Worker self.addEventListener("fetch",
function (event) {
console.log(event.request.url);
event.respondWith(
caches.match(event.request)
.then(function (response) {
if (response) {
return response;
}
return fetch(event.request)
.then(function (response) {
return response;
}).catch(function (error) {
throw error;
});
})
);
});
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Worker self.addEventListener("fetch",
function (event) {
console.log(event.request.url);
event.respondWith(
caches.match(event.request)
.then(function (response) {
if (response) {
return response;
}
return fetch(event.request)
.then(function (response) {
return response;
}).catch(function (error) {
throw error;
});
})
);
});
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Worker self.addEventListener("fetch",
function (event) {
console.log(event.request.url);
event.respondWith(
caches.match(event.request)
.then(function (response) {
if (response) {
return response;
}
return fetch(event.request)
.then(function (response) {
return response;
}).catch(function (error) {
throw error;
});
})
);
});
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Worker self.addEventListener("fetch",
function (event) {
console.log(event.request.url);
event.respondWith(
caches.match(event.request)
.then(function (response) {
if (response) {
return response;
}
return fetch(event.request)
.then(function (response) {
return response;
}).catch(function (error) {
throw error;
});
})
);
});
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Worker self.addEventListener("fetch",
function (event) {
console.log(event.request.url);
event.respondWith(
caches.match(event.request)
.then(function (response) {
if (response) {
return response;
}
return fetch(event.request)
.then(function (response) {
return response;
}).catch(function (error) {
throw error;
});
})
);
});
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Worker self.addEventListener("fetch",
function (event) {
console.log(event.request.url);
event.respondWith(
caches.match(event.request)
.then(function (response) {
if (response) {
return response;
}
return fetch(event.request)
.then(function (response) {
return response;
}).catch(function (error) {
throw error;
});
})
);
});
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@adunkman
“fetch” event
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@adunkman
Programmatic access to
browser cache
Replaces AppCache
Allows custom offline logic
Is completely encapsulated
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@adunkman
push, sync, fetch
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@adunkman
ServiceWorker
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@adunkman
HTTPS/localhost only
Not persistent
Not tied to browser
context
Domain events
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@adunkman
There’s more to the
web than web pages
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getharvest.com/careers
dunkman.me/talks/tabs
@adunkman