Author: Wushan Old Demon Background Writing Android asynchronous tasks in business has always been a challenge. The previous callback and thread management methods were complex and cumbersome, making the code difficult to maintain and read. JavaScript actually faces the same problem in the front-end field, and Promise is one of its more mainstream solutions. Before […]
Tag: promise
Explore synchronous and asynchronous, Ajax, callback functions, Promise
Table of Contents 1. Introduction to Ajax 1. The concept of asynchronous and synchronized 2. Why is it said that synchronous requests will “reload the entire page”, while asynchronous requests “will only load part of the page”. What does this mean? 3. Functions and advantages of Ajax Function Advantage 4.Why is Ajax called asynchronous javascript […]
Refactor Android asynchronous code using promises
Background Writing Android asynchronous tasks in business has always been a challenge. The previous callback and thread management methods were complex and cumbersome, making the code difficult to maintain and read. JavaScript actually faces the same problem in the front-end field, and Promise is one of its more mainstream solutions. Before trying to use Promise, […]
Concurrency control of Promise – from ordinary concurrency pool to dynamic concurrency pool
1. Scene You are given an array of 200 URLs. To send requests through these URLs, the number of concurrent requests cannot exceed five. This is a very common interview question. Next, let us learn about Promise concurrency control 2. Implementation of ordinary concurrent pool The main idea is to determine whether the current queue […]
33 concepts JavaScript developers should understand 12-Promise, async and wait
33 concepts JavaScript developers should understand 12-Promise, async and wait Directory call stack primitive type Value types and reference types Implicit, explicit, nominal and duck typing == and ===, typeof and instanceof this, call, apply and bind Function scope, block scope and lexical scope Closure Higher order functions such as map, reduce, filter etc. expressions […]
Promise: hand-tear promise
(1) Basic framework construction Pass a function executor into the promise. The executor accepts two parameters: resolve and reject. In new Promise, the executor will be automatically called. Handwritten promises are made through es6 classes. The corresponding myPromise class is as follows: class MyPromise { constructor(executor) { executor(this.resolve, this.reject)() } resolve(result) { } reject(result) { […]
Promise asynchronous processing method
A synchronous statement means that subsequent statements will not be executed until the execution of the statement is completed. An asynchronous statement means that after execution, the js engine will generate an asynchronous object. Mina’s statement will not wait for the asynchronous object to complete execution, but will be executed directly. Basically all operations of […]
NodeJS callback hell and Promise optimization
There are many asynchronous APIs in NodeJS, such as the common readFile method of the fs module. Although there is a synchronous version of readFileSync, its performance is definitely not as good as the former. So let’s start with the asynchronous version of readFile: const fs = require(‘fs’); fs.readFile(‘./a.txt’, ‘utf-8’, function(error, data) { if (!error) […]
A detailed study of Promise and related knowledge
Learn key phrases: Promise promise learning promise.all promise.race promise.resolve 1. Write in front Promise is something that cannot be avoided by the front end, so we must study it well. The purpose of writing this article is to deepen the learning and use of promise. 2. Start 2.1 Preparation First create a folder and create […]
How to customize the Promise function and detailed explanation
Customized Promise function There are three ways to change the state of Promise resolve(),reject(), throw exception The state of a Promise can only be modified once Execute the callback in the then method of Promise Asynchronous task then method implementation Specify multiple callbacks Implementation of results returned by then method under synchronization tasks catch method […]