letbar;// this has an asynchronous signature, but calls callback synchronouslyfunctionsomeAsyncApiCall(callback){callback();}// the callback is called before `someAsyncApiCall` completes.someAsyncApiCall(()=>{// since someAsyncApiCall has completed, bar hasn't been assigned any valueconsole....
letbar;// this has an asynchronous signature, but calls callback synchronouslyfunctionsomeAsyncApiCall(callback){callback();}// the callback is called before `someAsyncApiCall` completes.someAsyncApiCall(()=>{// since someAsyncApiCall has completed, bar hasn't been assigned any valueconsole....
// 改造2: 在doThing()上使用async/await,以确保load方法能同步拿到加载结果(async/await代码可读性优于Promise/then)才执行后续代码asyncfunctiondoThing(){// 3. 在需要时触发定义加载,如:key='TEST'letdef=awaitload('TEST')// 4. 满足预期:def不再为undefined,console.log(def)} 在Node.js的世界里,不...
// this has an asynchronous signature, but calls callback synchronously function someAsyncApiCall(callback){callback();} // the callback is called before `someAsyncApiCall` completes someAsyncApiCall(()=>{ console.log('bar',bar); }); bar = 1; 用户定义的someAsyncApiCall( )虽然从注释上...
事件循环是Node.js能够实现非阻塞I/O的基础,尽管JavaScript应用是单线程运行的,但是它可以将操作向下传递到系统内核去执行。 大多数现代系统内核都是支持多线程的,它们可以同时在后台处理多个操作。当其中任何一个任务完成后,内核会通知Node.js,这样它就可以把对应的回调函数添加进poll队列,回调函数最终就能够被执行,后...
(null, a + b); }) } // Run in a fiber Sync(function(){ // Function.prototype.sync() interface is same as Function.prototype.call() - first argument is 'this' context var result = asyncFunction.sync(null, 2, 3); console.log(result); // 5 // Read file synchronously without ...
This way, you can have an event loop that just calls an async function and handle the result of the async function in a callback, when it happens to be done. This is one of the major strengths of node.js, and one of the basic rules: "do not block the main event loop". Share ...
Since Node.js 8, you can do the following using async/await: const readline = require('readline'); const rl = readline.createInterface({ input: process.stdin, output: process.stdout }); function readLineAsync(message) { return new Promise((resolve, reject) => { rl.question(message, (ans...
When Node.js starts, it initializes the event loop, processes the provided input script (or drops into the REPL, which is not covered in this document) which may make async API calls, schedule timers, or call process.nextTick(), then begins processing the event loop. ...
typename...Args>FSReqBase*AsyncDestCall(Environment*env,FSReqBase*req_wrap,constv8::FunctionCall...