Plato on Github
Report Home
node_modules/selenium-webdriver/lib/goog/async/nexttick.js
Maintainability
70.29
Lines of code
198
Difficulty
34.22
Estimated Errors
1.21
Function weight
By Complexity
By SLOC
// Copyright 2013 The Closure Library Authors. All Rights Reserved. // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS-IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. /** * @fileoverview Provides a function to schedule running a function as soon * as possible after the current JS execution stops and yields to the event * loop. * */ goog.provide('goog.async.nextTick'); goog.provide('goog.async.throwException'); goog.require('goog.debug.entryPointRegistry'); goog.require('goog.functions'); goog.require('goog.labs.userAgent.browser'); /** * Throw an item without interrupting the current execution context. For * example, if processing a group of items in a loop, sometimes it is useful * to report an error while still allowing the rest of the batch to be * processed. * @param {*} exception */ goog.async.throwException = function(exception) { // Each throw needs to be in its own context. goog.global.setTimeout(function() { throw exception; }, 0); }; /** * Fires the provided callbacks as soon as possible after the current JS * execution context. setTimeout(…, 0) takes at least 4ms when called from * within another setTimeout(…, 0) for legacy reasons. * * This will not schedule the callback as a microtask (i.e. a task that can * preempt user input or networking callbacks). It is meant to emulate what * setTimeout(_, 0) would do if it were not throttled. If you desire microtask * behavior, use {@see goog.Promise} instead. * * @param {function(this:SCOPE)} callback Callback function to fire as soon as * possible. * @param {SCOPE=} opt_context Object in whose scope to call the listener. * @template SCOPE */ goog.async.nextTick = function(callback, opt_context) { var cb = callback; if (opt_context) { cb = goog.bind(callback, opt_context); } cb = goog.async.nextTick.wrapCallback_(cb); // window.setImmediate was introduced and currently only supported by IE10+, // but due to a bug in the implementation it is not guaranteed that // setImmediate is faster than setTimeout nor that setImmediate N is before // setImmediate N+1. That is why we do not use the native version if // available. We do, however, call setImmediate if it is a normal function // because that indicates that it has been replaced by goog.testing.MockClock // which we do want to support. // See // http://connect.microsoft.com/IE/feedback/details/801823/setimmediate-and-messagechannel-are-broken-in-ie10 if (goog.isFunction(goog.global.setImmediate) && (!goog.global.Window || goog.global.Window.prototype.setImmediate != goog.global.setImmediate)) { goog.global.setImmediate(cb); return; } // Look for and cache the custom fallback version of setImmediate. if (!goog.async.nextTick.setImmediate_) { goog.async.nextTick.setImmediate_ = goog.async.nextTick.getSetImmediateEmulator_(); } goog.async.nextTick.setImmediate_(cb); }; /** * Cache for the setImmediate implementation. * @type {function(function())} * @private */ goog.async.nextTick.setImmediate_; /** * Determines the best possible implementation to run a function as soon as * the JS event loop is idle. * @return {function(function())} The "setImmediate" implementation. * @private */ goog.async.nextTick.getSetImmediateEmulator_ = function() { // Create a private message channel and use it to postMessage empty messages // to ourselves. var Channel = goog.global['MessageChannel']; // If MessageChannel is not available and we are in a browser, implement // an iframe based polyfill in browsers that have postMessage and // document.addEventListener. The latter excludes IE8 because it has a // synchronous postMessage implementation. if (typeof Channel === 'undefined' && typeof window !== 'undefined' && window.postMessage && window.addEventListener) { /** @constructor */ Channel = function() { // Make an empty, invisible iframe. var iframe = document.createElement('iframe'); iframe.style.display = 'none'; iframe.src = ''; document.documentElement.appendChild(iframe); var win = iframe.contentWindow; var doc = win.document; doc.open(); doc.write(''); doc.close(); // Do not post anything sensitive over this channel, as the workaround for // pages with file: origin could allow that information to be modified or // intercepted. var message = 'callImmediate' + Math.random(); // The same origin policy rejects attempts to postMessage from file: urls // unless the origin is '*'. // TODO(b/16335441): Use '*' origin for data: and other similar protocols. var origin = win.location.protocol == 'file:' ? '*' : win.location.protocol + '//' + win.location.host; var onmessage = goog.bind(function(e) { // Validate origin and message to make sure that this message was // intended for us. if (e.origin != origin && e.data != message) { return; } this['port1'].onmessage(); }, this); win.addEventListener('message', onmessage, false); this['port1'] = {}; this['port2'] = { postMessage: function() { win.postMessage(message, origin); } }; }; } if (typeof Channel !== 'undefined' && // Exclude all of IE due to // http://codeforhire.com/2013/09/21/setimmediate-and-messagechannel-broken-on-internet-explorer-10/ // which allows starving postMessage with a busy setTimeout loop. // This currently affects IE10 and IE11 which would otherwise be able // to use the postMessage based fallbacks. !goog.labs.userAgent.browser.isIE()) { var channel = new Channel(); // Use a fifo linked list to call callbacks in the right order. var head = {}; var tail = head; channel['port1'].onmessage = function() { head = head.next; var cb = head.cb; head.cb = null; cb(); }; return function(cb) { tail.next = { cb: cb }; tail = tail.next; channel['port2'].postMessage(0); }; } // Implementation for IE6+: Script elements fire an asynchronous // onreadystatechange event when inserted into the DOM. if (typeof document !== 'undefined' && 'onreadystatechange' in document.createElement('script')) { return function(cb) { var script = document.createElement('script'); script.onreadystatechange = function() { // Clean up and call the callback. script.onreadystatechange = null; script.parentNode.removeChild(script); script = null; cb(); cb = null; }; document.documentElement.appendChild(script); }; } // Fall back to setTimeout with 0. In browsers this creates a delay of 5ms // or more. return function(cb) { goog.global.setTimeout(cb, 0); }; }; /** * Helper function that is overrided to protect callbacks with entry point * monitor if the application monitors entry points. * @param {function()} callback Callback function to fire as soon as possible. * @return {function()} The wrapped callback. * @private */ goog.async.nextTick.wrapCallback_ = goog.functions.identity; // Register the callback function as an entry point, so that it can be // monitored for exception handling, etc. This has to be done in this file // since it requires special code to handle all browsers. goog.debug.entryPointRegistry.register( /** * @param {function(!Function): !Function} transformer The transforming * function. */ function(transformer) { goog.async.nextTick.wrapCallback_ = transformer; });