'use strict';
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var callable, byObserver;
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callable = function (fn) {
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if (typeof fn !== 'function') throw new TypeError(fn + " is not a function");
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return fn;
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};
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byObserver = function (Observer) {
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var node = document.createTextNode(''), queue, currentQueue, i = 0;
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new Observer(function () {
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var callback;
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if (!queue) {
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if (!currentQueue) return;
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queue = currentQueue;
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} else if (currentQueue) {
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queue = currentQueue.concat(queue);
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}
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currentQueue = queue;
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queue = null;
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if (typeof currentQueue === 'function') {
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callback = currentQueue;
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currentQueue = null;
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callback();
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return;
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}
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node.data = (i = ++i % 2); // Invoke other batch, to handle leftover callbacks in case of crash
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while (currentQueue) {
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callback = currentQueue.shift();
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if (!currentQueue.length) currentQueue = null;
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callback();
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}
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}).observe(node, { characterData: true });
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return function (fn) {
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callable(fn);
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if (queue) {
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if (typeof queue === 'function') queue = [queue, fn];
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else queue.push(fn);
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return;
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}
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queue = fn;
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node.data = (i = ++i % 2);
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};
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};
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module.exports = (function () {
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// Node.js
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if ((typeof process === 'object') && process && (typeof process.nextTick === 'function')) {
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return process.nextTick;
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}
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// MutationObserver
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if ((typeof document === 'object') && document) {
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if (typeof MutationObserver === 'function') return byObserver(MutationObserver);
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if (typeof WebKitMutationObserver === 'function') return byObserver(WebKitMutationObserver);
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}
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// W3C Draft
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// http://dvcs.w3.org/hg/webperf/raw-file/tip/specs/setImmediate/Overview.html
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if (typeof setImmediate === 'function') {
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return function (cb) { setImmediate(callable(cb)); };
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}
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// Wide available standard
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if ((typeof setTimeout === 'function') || (typeof setTimeout === 'object')) {
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return function (cb) { setTimeout(callable(cb), 0); };
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}
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return null;
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}());
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