javascript promises tutorial

to read, followed by strong coupling, and the interface becomes poorly expanded. We need a pattern to solve this problem, and that's what promises is going to do.Asynchronous function typeThe asynchronous functions in JavaScript can be divided into two main types: I/O functions (Ajax, Script ... ） Timing Functions (SetTimeout, setinterval, Setimmediate) Asynchronous function Exception cap

Many languages, in order to handle asynchronous patterns more like the usual order, contain an interesting library of scenarios called Promises,deferreds, or futures. The promises of JavaScript can facilitate separation of concerns in place of tightly coupled interfaces. This article is about JavaScript

(function (Resolve) {resolve (100);}); Promise.then (function (value) {return value * *;}). Then (function (value) {return value * *;}). Then (function (value) {Console.log (value);//= + 100 * 2 * 2});　　Promises Error HandlingThe then () function receives two callback functions as arguments. The function that the second callback function fires when promise becomes rejected. Promise also provides a catch () function to handle the rejected state of pro

Asynchronous programming in Javascript is gradually accepted by everyone. Previously, it was generally implemented through callback nesting, setTimeout, setInterval, and other methods. The code looks very inintuitive and difficult to understand without looking at the entire code logic. Asynchronous functions in Javascript include I/O functions (Ajax, postMessage, img load, script load, etc.) and time functi

(URL, params) { returnfunction(PRE) { varNew Promise (); function (data) { promise.resolved (data); }); return promise;} ;} function begin (Value) { return value + '! ' ;}Initialization code:var New Promise (BEGIN);p Romise.then (Nest2 (' promise.php ', {a:1})) . Then (Nest2 (' promise.php ', {b:2 });p romise.resolved (' start ');It can also be called in a different way, so that there are multiple values in the internal _resloves queueNew Promise (begin);Promise.then (Nes

value * *;}). Then (function (value) { return value * *;}). Then (function (value) { console.log (value);//= + 100 * 2 * 2});The Promises error handling then () function receives two callback functions as arguments. The function that the second callback function fires when promise becomes rejected. Promise also provides a catch () function to handle the rejected state of promise. Look at the following code:Promise.then (fucntion (Result) {

Translation: JavaScript Promises and AngularJS $q ServiceOriginal: http://www.webdeveasy.com/javascript-promises-and-angularjs-q-service/Original date: September 30, 2014A promise (delay) is a simple and powerful way to handle asynchronous development. CommonJS Wikipedia lists the implementation proposals for several p

();}); Promise.then (function (value) { return value * *;}). Then (function (value) { return value * *;}). Then (function (value) { ?　　Promises? error handling ?The then () function receives two callback functions as a parameter.The function that the second callback function fires when promise becomes rejected.Promise also provides a catch () function to handle the rejected state of promise.Look at the following code:Promise.then (fucnti

This article describes the asynchronous programming specification PromisesA in Javascript in detail, and describes Deferred and Promises in jQuery. For more information, see asynchronous programming in Javascript, previously, it was generally implemented through callback nesting, setTimeout, setInterval, and other methods. The code looks very inintuitive and it i

JavaScript asynchronous programming is gradually accepted by everyone, previously we generally through callback nesting, settimeout, setinterval, etc., the code looks very intuitive, do not look at the entire code logic is difficult to quickly understand. In JavaScript, asynchronous functions may have I/O functions (Ajax, PostMessage, img load, script load, etc.), timer functions (settimeout, setinterval),

The JavaScript language execution environment is "single thread"Only one task can be completed at a time. If you have multiple tasks, you must queue, complete the previous task, and then perform the latter taskThe JavaScript language divides the execution pattern of a task into two types: synchronous (synchronous) and asynchronous (asynchronous)"Asynchronous mode" is completely different, each task has one

The Promise object is used for deferred (deferred) and asynchronous (asynchronous) computations. This article mainly and everybody to share javascript/node.js in the promises detailed, hoped can help everybody. One Promise in one of the following three states: Pending: Initial state, non-fulfilled or rejected. Fulfilled: successful operation. Rejected: failed operation. The Promise interfac

How to Use Promises to write more elegant JavaScript code, promisesjavascript You may have accidentally heard of Promises. Many people are discussing it and using it, but you don't know why they are so special. Can't you use callback? What's special? In this article, let's take a look at what Promises are and how to us

You may have overheard promises, a lot of people are talking about it, using it, but you don't know why they're so special. Can't you use a callback? What's so special about it? In this article, let's look at what promises is and how to use them to write more elegant JavaScript code. Promises easy to read For example

Initial JavaScript Promises IIError Handling in asynchronous programming is human and ideal, just as many programming languages have implemented the following error handling methods: try {var val = JSON. parse (fs. readFileSync ("file. json ");} catch (SyntaxError e) {// json syntax error console. error ("not in json format");} catch (Error e) {// other types of error console. error ("file cannot be read")}

This article mainly introduces the use of Promise in JavaScript. This article first introduces the relevant Promises specifications, and then explains a mini Promises to deepen understanding, interested friends can refer to the Javascript callback function (callback) to process asynchronous programming. From Synchronou

JavaScript: elementary JavaScript tutorial (6). The Javascript tutorial uses the internal Object System of the browser to interact with HTML documents. It is used to organize and package related elements for program designers, so as to reduce the work of programmers and impr

Reference Type of the JavaScript getting started tutorial and javascript getting started tutorial Reference Type A reference type is a data structure used to organize data and functions together. It is also often called a class, but this name is not appropriate. Although ECMAScript is technically an object-oriented lan

JavaScript Tutorial Series 49:javascript Tutorial: The prototype chain is immutable