个人中心
gpt4 book ai didi

javascript - setTimeout(0) vs window.postMessage vs MessagePort.postMessage

转载 作者：太空狗 更新时间：2023-10-29 15:50:27 34 4
gpt4 key购买 nike

显然，使用 window.postMessage是 preferred way在所有现代浏览器中通过 window.setTimeout(fn, 0) 对异步 javascript 回调进行排队。我找不到 window.postMessage 之间的类似比较和 MessagePort.postMessage (使用相同的 MessageChannel 异步发送和接收消息)。有没有人看过或做过任何计时？是否MessagePort.postMessage是否为此目的而工作(如有)？

[EDITED] MessagePort.postMessage 确实适用于此，但 window.postMessage 仍然是首选方式，IMO(请参阅我的回答) .

最佳答案

[更新] 添加了 setImmediate 的测试和一个 JSFiddle 。相关的，有一个cross-browser implementation setImmediate 和 ASAP library被 Q 使用 promise 解决/拒绝。

我继续使用 David Baron's code 的修改版本做了一些计时，结果如下:

setTimeoutMC - 使用MessageChannel
setTimeoutPM - 使用window.postMessage
setTimeout(0) - 使用setTimer

IE10:

2000 iterations of setTimeoutMC took 126 milliseconds.
2000 iterations of setTimeoutPM took 190 milliseconds.
2000 iterations of setTimeout(0) took 7986 milliseconds.

Chrome v29.0.1547.66:

2000 iterations of setTimeoutMC took 144 milliseconds.
2000 iterations of setTimeoutPM took 81 milliseconds.
2000 iterations of setTimeout(0) took 10589 milliseconds.

很明显，window.postMessage是这里的赢家(考虑到现有的跨浏览器支持水平)。较宽松的是 window.setTimeout(fn, 0)，应尽可能避免。

代码:

<!DOCTYPE html>
<html>
<head>
    <!-- http://stackoverflow.com/q/18826570/1768303 -->
    <!-- based on http://dbaron.org/log/20100309-faster-timeouts -->
    <!-- requires IE10 or Chrome. Firefox doesn't support MessageChannel yet -->
    <title></title>
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <script type="text/javascript">

        // setTimeoutMC via MessageChannel

        (function () {
            "use strict";
            var i = 0;
            var timeouts = {};
            var setApiName = "setTimeoutMC";
            var clearApiName = "clearTimeoutMC";

            var channel = new MessageChannel();

            function post(fn) {
                if (i === 0x100000000) // max queue size
                    i = 0;
                if (++i in timeouts)
                    throw new Error(setApiName + " queue overflow.");
                timeouts[i] = fn;
                channel.port2.postMessage(i);
                return i;
            }

            channel.port1.onmessage = function (ev) {
                var id = ev.data;
                var fn = timeouts[id];
                if (fn) {
                    delete timeouts[id];
                    fn();
                }
            }

            function clear(id) {
                delete timeouts[id];
            }

            channel.port1.start();
            channel.port2.start();

            window[setApiName] = post;
            window[clearApiName] = clear;
        })();

        // setTimeoutPM via window.postMessage

        (function () {
            "use strict";
            var i = 0;
            var timeouts = {};
            var setApiName = "setTimeoutPM";
            var clearApiName = "clearTimeoutPM";
            var messageName = setApiName + new Date().getTime();

            function post(fn) {
                if (i === 0x100000000) // max queue size
                    i = 0;
                if (++i in timeouts)
                    throw new Error(setApiName + " queue overflow.");
                timeouts[i] = fn;
                window.postMessage({ type: messageName, id: i }, "*");
                return i;
            }

            function receive(ev) {
                if (ev.source !== window)
                    return;
                var data = ev.data;
                if (data && data instanceof Object && data.type === messageName) {
                    ev.stopPropagation();
                    var id = ev.data.id;
                    var fn = timeouts[id];
                    if (fn) {
                        delete timeouts[id];
                        fn();
                    }
                }
            }

            function clear(id) {
                delete timeouts[id];
            }

            window.addEventListener("message", receive, true);
            window[setApiName] = post;
            window[clearApiName] = clear;
        })();

        // timing

        function runtest() {
            var output = document.getElementById("output");
            var outputText = document.createTextNode("");
            output.appendChild(outputText);
            function printOutput(line) {
                outputText.data += line + "\n";
            }

            var n = 2000;
            var i = 0;
            var startTime = Date.now();
            setTimeoutMC(testMC);

            function testMC() {
                if (++i === n) {
                    var endTime = Date.now();
                    printOutput(n + " iterations of setTimeoutMC took " + (endTime - startTime) + " milliseconds.");
                    i = 0;
                    startTime = Date.now();
                    setTimeoutPM(testPM, 0);
                } else {
                    setTimeoutMC(testMC);
                }
            }

            function testPM() {
                if (++i === n) {
                    var endTime = Date.now();
                    printOutput(n + " iterations of setTimeoutPM took " + (endTime - startTime) + " milliseconds.");
                    i = 0;
                    startTime = Date.now();
                    setTimeout(test, 0);
                } else {
                    setTimeoutPM(testPM);
                }
            }

            function test() {
                if (++i === n) {
                    var endTime = Date.now();
                    printOutput(n + " iterations of setTimeout(0) took " + (endTime - startTime) + " milliseconds.");
                }
                else {
                    setTimeout(test, 0);
                }
            }
        }
    </script>
</head>

<body onload="runtest()">
    <pre id="output"></pre>
</body>
</html>

关于javascript - setTimeout(0) vs window.postMessage vs MessagePort.postMessage，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18826570/

34 4 0
文章推荐： javascript - 延迟动态添加的 Javascript
文章推荐： c - 从字符串中读取数字列表
文章推荐： c - c中普通指针和const指针的区别
文章推荐： Android数据绑定(bind)两种方式的转换方式
太空狗
个人简介

我是一名优秀的程序员,十分优秀！

滴滴打车优惠券免费领取
滴滴打车优惠券
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com