//`eventLoop` is an array that acts as a queue队列,先排队的先办理vareventLoop =[ ];varevent;//keep going "forever"while(true) {//perform a "tick"if(eventLoop.length > 0) {//get the next event in the queueevent =eventLoop.shift();//now, execute the next eventtry{ event(); }...
Chapter 1. Asynchrony: Now & Later One of the most important and yet often misunderstood parts of programming in a language like JavaScript is how to express and manipulate program … - Selection from You Don't Know JS: Async & Performance [Book]
因为0毫秒的话由于浏览器渲染太快,录屏不好捕捉,我又没啥录屏慢放的工具,大家可以自行测试的,结果也是一样,最安全的方法是写一个index.html文件,在这个文件中插入上面的js脚本,然后浏览器打开,谷歌下使用控制台中performance功能查看一帧一帧的加载最为恰当,不过这样录屏不好录所以。。。
检查没有微任务,第三次Event Loop结束 执行timer3,console.log(5)同步任务,直接执行,打印5 检查没有微任务,第四次Event Loop结束 执行timer1,console.log(2)同步任务,直接执行,打印2 检查没有微任务,也没有宏任务,第五次Event Loop结束 结果:1,4,8,7,3,6,5,2 提一下NodeJS中的运行机制 上面的一切都是...
Since node@10.0.0, there is support for async iterators and the related for-await-of loop. These come in handy when the actual values we iterate over, and the end state of the iteration, are not known by the time the iterator method returns – mostly when working with streams. Aside fr...
Node.js 还提供了perf_hooks模块,可以通过performance.eventLoopUtilization()来检查事件循环的利用率。开发者可以通过不断采样获取事件循环的使用情况,从而判断是否存在 high event loop utilization 现象。 const{performance,PerformanceObserver}=require('perf_hooks');constelu=performance.eventLoopUtilization();setInterv...
该API 还提供了一种在程序运行期间精确标记时间点的方法。我们可以使用performance.mark方法获取高精度事件的时间戳,例如循环迭代的开始时间。 运行下面代码: 复制 let start_mark = performance.mark("loop_start", {detail:"starting loop of 1000 iterations"} ...
keep_infinity (default: false)— Pass true to prevent Infinity from being compressed into 1/0, which may cause performance issues on Chrome. loops (default: true)— optimizations for do, while and for loops when we can statically determine the condition. merge_vars (default: true)— combine...
Track events with VideoJS and keep an eye on performance metrics videojs-standard 11289.1.0 JavaScript style for plugins and tools in the video.js ecosystem. jb-videojs-hls-quality-selector 15762.0.2 Adds a quality selector menu for HLS sources played in videojs. Requires `videojs-contrib-...
Promise 是解决回调嵌套地狱的灵丹妙药,特别是当自从 async/await 全面普及之后,它们的组合无疑成为了 JavaScript 异步编程的终极解决方案,现在大量的项目都已经开始使用这种模式。 但是优雅的语法后面也隐藏着性能损耗,我们可以使用 github 上一个已有的跑分项目:https:///kyrylkov/promise-async-performance进行测试,以...