bluebird/js/zalgo/schedule.js

Full featured Promises/A+ implementation with exceptionally good performance

/**
 * Copyright (c) 2013 Petka Antonov
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:</p>
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
"use strict";
var global = require("./global.js");
var ASSERT = require("./assert.js");
var schedule;
if( typeof process !== "undefined" && process !== null &&
    typeof process.cwd === "function" ) {
    if( typeof global.setImmediate !== "undefined" ) {
        schedule = function Promise$_Scheduler( fn ) {
            global.setImmediate( fn );
        };
    }
    else {
        schedule = function Promise$_Scheduler( fn ) {
            process.nextTick( fn );
        };
    }
}
else if( ( typeof MutationObserver === "function" ||
        typeof WebkitMutationObserver === "function" ||
        typeof WebKitMutationObserver === "function" ) &&
        typeof document !== "undefined" &&
        typeof document.createElement === "function" ) {


    schedule = (function(){
        var MutationObserver = global.MutationObserver ||
            global.WebkitMutationObserver ||
            global.WebKitMutationObserver;
        var div = document.createElement("div");
        var queuedFn = void 0;
        var observer = new MutationObserver(
            function Promise$_Scheduler() {
                var fn = queuedFn;
                queuedFn = void 0;
                fn();
            }
        );
        var cur = true;
        observer.observe( div, {
            attributes: true,
            childList: true,
            characterData: true
        });
        return function Promise$_Scheduler( fn ) {
            queuedFn = fn;
            cur = !cur;
            div.setAttribute( "class", cur ? "foo" : "bar" );
        };

    })();
}
else if ( typeof global.postMessage === "function" &&
    typeof global.importScripts !== "function" &&
    typeof global.addEventListener === "function" &&
    typeof global.removeEventListener === "function" ) {

    var MESSAGE_KEY = "bluebird_message_key_" + Math.random();
    schedule = (function(){
        var queuedFn = void 0;

        function Promise$_Scheduler(e) {
            if(e.source === global &&
                e.data === MESSAGE_KEY) {
                var fn = queuedFn;
                queuedFn = void 0;
                fn();
            }
        }

        global.addEventListener( "message", Promise$_Scheduler, false );

        return function Promise$_Scheduler( fn ) {
            queuedFn = fn;
            global.postMessage(
                MESSAGE_KEY, "*"
            );
        };

    })();
}
else if( typeof MessageChannel === "function" ) {
    schedule = (function(){
        var queuedFn = void 0;

        var channel = new MessageChannel();
        channel.port1.onmessage = function Promise$_Scheduler() {
                var fn = queuedFn;
                queuedFn = void 0;
                fn();
        };

        return function Promise$_Scheduler( fn ) {
            queuedFn = fn;
            channel.port2.postMessage( null );
        };
    })();
}
else if( global.setTimeout ) {
    schedule = function Promise$_Scheduler( fn ) {
        setTimeout( fn, 4 );
    };
}
else {
    schedule = function Promise$_Scheduler( fn ) {
        fn();
    };
}

module.exports = schedule;