84 lines
2.6 KiB
JavaScript
84 lines
2.6 KiB
JavaScript
// from https://gist.github.com/inexorabletash/52f437d1451d12145264
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(function(global) {
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var channels = [];
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function BroadcastChannel(channel) {
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var $this = this;
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channel = String(channel);
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var id = '$BroadcastChannel$' + channel + '$';
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channels[id] = channels[id] || [];
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channels[id].push(this);
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this._name = channel;
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this._id = id;
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this._closed = false;
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this._mc = new MessageChannel();
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this._mc.port1.start();
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this._mc.port2.start();
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global.addEventListener('storage', function(e) {
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if (e.storageArea !== global.localStorage) return;
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if (e.newValue === null) return;
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if (e.key.substring(0, id.length) !== id) return;
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var data = JSON.parse(e.newValue);
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$this._mc.port2.postMessage(data);
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});
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}
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BroadcastChannel.prototype = {
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// BroadcastChannel API
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get name() { return this._name; },
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postMessage: function(message) {
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var $this = this;
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if (this._closed) {
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var e = new Error();
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e.name = 'InvalidStateError';
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throw e;
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}
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var value = JSON.stringify(message);
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// Broadcast to other contexts via storage events...
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var key = this._id + String(Date.now()) + '$' + String(Math.random());
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global.localStorage.setItem(key, value);
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setTimeout(function() { global.localStorage.removeItem(key); }, 500);
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// Broadcast to current context via ports
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channels[this._id].forEach(function(bc) {
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if (bc === $this) return;
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bc._mc.port2.postMessage(JSON.parse(value));
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});
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},
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close: function() {
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if (this._closed) return;
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this._closed = true;
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this._mc.port1.close();
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this._mc.port2.close();
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var index = channels[this._id].indexOf(this);
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channels[this._id].splice(index, 1);
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},
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// EventTarget API
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get onmessage() { return this._mc.port1.onmessage; },
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set onmessage(value) { this._mc.port1.onmessage = value; },
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addEventListener: function(type, listener /*, useCapture*/) {
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return this._mc.port1.addEventListener.apply(this._mc.port1, arguments);
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},
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removeEventListener: function(type, listener /*, useCapture*/) {
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return this._mc.port1.removeEventListener.apply(this._mc.port1, arguments);
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},
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dispatchEvent: function(event) {
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return this._mc.port1.dispatchEvent.apply(this._mc.port1, arguments);
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}
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};
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if (global.BroadcastChannel) {
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console.log("already has native BroadcastChannel");
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} else {
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global.BroadcastChannel = BroadcastChannel;
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console.log("use polyfill for BroadcastChannel");
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}
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}(window.top));
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