phpsleep3000技巧_javascript中怎么实现sleep函数

console.log('1', new Date())sleep(2000)console.log('1', new Date())

当然这个实际是没法实行的，由于JavaScript中没有sleep函数。
下面我们来几个方法实现之。

console.time('runTime:');setTimeout(function () { console.log('1', new Date()) setTimeout(function () { console.log('2', new Date()); setTimeout(function () { console.log('3', new Date()); console.timeEnd('runTime:'); }, 2000); }, 3000);}, 2000);// 输出如下：// 1 2022-09-18T01:25:48.317Z// 2 2022-09-18T01:25:51.333Z// 3 2022-09-18T01:25:53.341Z// runTime:: 7.038s

这段代码是不是看的很晕，嵌套的太麻烦了

function sleep(time) { var timeStamp = new Date().getTime(); var endTime = timeStamp + time; while (true) { if (new Date().getTime() > endTime) { return; } }}console.time('runTime:');sleep(2000);console.log('1', new Date());sleep(3000);console.log('2', new Date());sleep(2000);console.log('3', new Date());console.timeEnd('runTime:');// 输出如下// 1 2022-09-18T01:29:19.529Z// 2 2022-09-18T01:29:22.534Z// 3 2022-09-18T01:29:24.536Z// runTime:: 7.008s

这个方法由于有短期无限去世循环，会让全体程序假去世，页面也会假去世，不具备实用代价

function sleep(time) { return new Promise(function (resolve) { setTimeout(resolve, time); });}console.time('runTime:');console.log('1', new Date());sleep(1000).then(function () { console.log('2', new Date()); sleep(2000).then(function () { console.log('3', new Date()); console.timeEnd('runTime:'); });});console.log('a', new Date());// 输出如下：// 1 2022-09-18T01:32:40.420Z// a 2022-09-18T01:32:40.425Z// 2 2022-09-18T01:32:41.439Z// 3 2022-09-18T01:32:43.45基于async, promise 的sleep

// 还是这个看起来最简洁好用function sleep(time) { return new Promise((resolve) => setTimeout(resolve, time));}async function run() { console.time('runTime:'); console.log('1', new Date()); await sleep(2000); console.log('2', new Date()); await sleep(1000); console.log('3', new Date()); console.timeEnd('runTime:');}run();console.log('a', new Date());// 输出如下：// 1 2022-09-18T01:35:17.775Z// a 2022-09-18T01:35:17.779Z// 2 2022-09-18T01:35:19.790Z// 3 2022-09-18T01:35:20.802Z// runTime:: 3.027s使⽤child_process（⼦进程）实现sleep函数

var childProcess = require('child_process');var nodeBin = process.argv[0];function sleep(time) {childProcess.execFileSync(nodeBin, ['-e', 'setTimeout(function() {}, ' + time + ');']); // spawnSync函数 也可以// childProcess.spawnSync(nodeBin, ['-e', 'setTimeout(function() {}, ' + time + ');']);}console.time('runTime:');console.log('1', new Date());sleep(1000);console.log('2', new Date());sleep(2000);console.log('3', new Date());console.timeEnd('runTime:');// 输出如下：// 1 2022-09-18T01:37:50.387Z// 2 2022-09-18T01:37:51.445Z// 3 2022-09-18T01:37:53.500Z// runTime:: 3.113s

以上代码，是通过childProcess工具的execFileSync或者spawnSync创建⼀个同步进程，在同步进程中执⾏定时器，定时器执⾏完毕后回收进程，程序连续执⾏。

var sleep = require('sleep');console.log('1', new Date());console.time('runTime:');sleep.sleep(2); //休眠2秒钟console.log('2', new Date());sleep.msleep(1000); //休眠1000毫秒console.log('3', new Date());sleep.usleep(1000000) //休眠1000000微秒 = 1秒console.log('4', new Date());console.timeEnd('runTime:');// 输出如下：// 1 2022-09-18T01:42:07.302Z// 2 2022-09-18T01:42:09.311Z// 3 2022-09-18T01:42:10.320Z// 4 2022-09-18T01:42:11.334Z// runTime:: 4.028s

这个sleep支持了好几种韶光类型，很棒，但是缺陷是它是利用c++编写，某些环境下须要安装其他依赖才能支持。
比如在winserver 2008下就不能用了。

总结：多种方法，最简洁的还是 promise+ async 。