Usepromisesto Wait for a Function to Finish in JavaScript Apromiseis an object representing the eventual fulfillment or failure of an asynchronous operation. We attach the fulfillment callback to thepromisewith one or morethenstatements, and when can call the error handler callback in thecatch. ...
In the example, we wait for all promises to finish and in the end, we calculate the sum of returned values. $ node all.js finished 600 JS multiple requests with axios In the next example, we use the axois library to execute multiple get requests. Axios is a promise-based HTTP client ...
我们可以使用Promise.all,它通常在启动多个异步任务并发运行并为其结果创建承诺之后使用,以便人们可以等待所有任务完成。 const axios = require('axios'); const bitcoinPromise = axios.get('https://api.coinpaprika.com/v1/coins/btc-bitcoin/markets'); const dollarPromise = axios.get('https://api.exchange...
我们可以使用Promise.all,它通常在启动多个异步任务并发运行并为其结果创建承诺之后使用,以便人们可以等待所有任务完成。 const axios = require('axios'); const bitcoinPromise = axios.get('https://api.coinpaprika.com/v1/coins/btc-bitcoin/markets'); const dollarPromise = axios.get('https://api.exchange...
技术社区 JavaScript中的异步编程 1.同步与异步2.异步编程的实现3.回调函数4.Promise对象5.Async与await6.for...of循环1.同步与异步同步:每条指令都会严格按照他们出现的顺序来执行,是连续执行的。 异步:类似于系统中断,… lynch发表于前端 深入浅出JavaScript异步编程 Sky.G...发表于路演前端打开...
重写代码以使用async/await。这在解决您的原始问题之外还有一些好处：
const { parentPort } = require('worker_threads'); const delay = require('delay'); const ms = require('ms'); (async () => { // wait for a promise to finish await delay(ms('10s')); // signal to parent that the job is done if (parentPort) parentPort.postMessage('done'); ...
// In this function, p is a promise. We wait for it to finish, // then run fetchMessages(). const obj = await p; const data = await fetchMessages(username); return { ...obj, [username]: data}; } const msgObj = userList ...
1.1 如何将现有的回调 API 转换为 Promise? 我们可以使用 Promise 构造函数将回调转换为 Promise。 Promise 构造函数接受一个回调,带有两个参数resolve和reject。 Resolve:是在异步操作完成时应调用的回调。 Reject:是发生错误时要调用的回调函数。 构造函数立即返回一个对象,即 Promise 实例。 当在 promise 实例中使...
promises and then does something only after they have all been settled. From all the promises you enter into it, it creates a new promise which then waits for each promise to finish, before continuing. That ultimately means you can wait for multiple things to finish before you fire something...