70 lines
1.8 KiB
JavaScript
70 lines
1.8 KiB
JavaScript
'use strict';
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var Mutation = global.MutationObserver || global.WebKitMutationObserver;
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var scheduleDrain;
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{
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if (Mutation) {
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var called = 0;
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var observer = new Mutation(nextTick);
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var element = global.document.createTextNode('');
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observer.observe(element, {
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characterData: true
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});
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scheduleDrain = function () {
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element.data = (called = ++called % 2);
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};
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} else if (!global.setImmediate && typeof global.MessageChannel !== 'undefined') {
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var channel = new global.MessageChannel();
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channel.port1.onmessage = nextTick;
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scheduleDrain = function () {
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channel.port2.postMessage(0);
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};
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} else if ('document' in global && 'onreadystatechange' in global.document.createElement('script')) {
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scheduleDrain = function () {
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// Create a <script> element; its readystatechange event will be fired asynchronously once it is inserted
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// into the document. Do so, thus queuing up the task. Remember to clean up once it's been called.
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var scriptEl = global.document.createElement('script');
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scriptEl.onreadystatechange = function () {
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nextTick();
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scriptEl.onreadystatechange = null;
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scriptEl.parentNode.removeChild(scriptEl);
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scriptEl = null;
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};
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global.document.documentElement.appendChild(scriptEl);
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};
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} else {
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scheduleDrain = function () {
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setTimeout(nextTick, 0);
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};
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}
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}
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var draining;
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var queue = [];
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//named nextTick for less confusing stack traces
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function nextTick() {
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draining = true;
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var i, oldQueue;
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var len = queue.length;
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while (len) {
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oldQueue = queue;
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queue = [];
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i = -1;
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while (++i < len) {
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oldQueue[i]();
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}
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len = queue.length;
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}
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draining = false;
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}
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module.exports = immediate;
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function immediate(task) {
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if (queue.push(task) === 1 && !draining) {
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scheduleDrain();
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}
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}
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