js promise

(function(results) { returnresults[0].save({ key: value });}).then(function(result) { // the object was saved.},function(error) { // there was some error.}); Generally, developers think that an asynchronous promise failure is equivalent to throwing an exception. In fact, if a callback throws an error, promise returns the failure message. Passing an error to the next available error processor is equivalent t

exception, and when dealing with a remote object we can think of him as a proxy for a remote object. If promise is also a kind of asynchronous processing, then we will think of it and XHR and $.ajax what is the difference? It is customary for JS to use closures or callbacks to correspond to data returned asynchronously, such as a XHR request after a page is loaded. We can interact with the data as if it h

returned data If you fail to invoke the Reject () method of the deferred object, parameter: The returned data Returns the Deferred.promise object Invoke the Ajax () method to get the Promise object, parameter: URL, Call the Promise object's then () method, parameter: anonymous function Call the Ajax () method, get to the Promise object, return this object

(this.resolve)3. Execute Promisecallback Our logic jumps to the inside of the Promisecallback function.setTimeout(() => { resolve("延时执行")}, 1000)Logic is simple, is to wait 1 seconds after the execution of the Resolve function, which resolve?Promisecallback (Resolve), FN (this.resolve), resolve4. Execute resolve our logic jumps to the inside of the resolve function.that.cb(data)Where does this that.cb come from? is the callback function in the then parenthesis that we saved in the first step, w

IntroductionIn the classic article about Deferred usage in jQuery1.5 (for the translation, see here), we will provide the following description:$. Ajax () returns an object packed with other deferred-related methods. I discussed promise (), but you'll also find then (), success (), error (), and a host of others. you don't have access to the complete deferred object, though; only the promise, callback-bindi

promise object in JavaScript Many people who do the front end should have heard of promise (or deferred) objects, today I will tell about my understanding of promise What? Promise is one of the COMMONJS specifications, with resolve, reject, done, fail, then and other methods, can help us control the flow of code, t

libraries, and should.js is one of them. In the code above, a BDD-style assertion is implemented using Should.js.Next, we perform the tests:$ Mocha Test/chapter1/synchronous.jsWe will see the following output: Calculator #add ? 1 + 2 = 3 ? 2-1 = 1 2 passing (9MS)Asynchronous code (callback) testWhen you say JavaScript, you must have a callback function. From the front-end Ajax communication to node. JS asynchronous data access, the cal

1 Promise Overview The Promise object is a specification proposed by the COMMONJS workgroup to provide a unified interface for asynchronous operations. So, what is promises. First, it is an object, that is, the use of other JavaScript objects, and second, it acts as an agent (proxy), acting as an intermediary between an asynchronous operation and a callback function. It enables the asynchronous operation t

libraries, and should.js is one of them. In the code above, a BDD-style assertion is implemented using Should.js.Next, we perform the tests:$ Mocha Test/chapter1/synchronous.jsWe will see the following output: Calculator #add ? 1 + 2 = 3 ? 2-1 = 1 2 passing (9MS)Asynchronous code (callback) testWhen you say JavaScript, you must have a callback function. From the front-end Ajax communication to node. JS asynchronous data access, the cal

Preface What is to be said here is a redux in the react of the application of the problem, talk about Redux,react-redux,redux-thunk,redux-actions,redux-promise, Redux-sage the effects of these packages and the problems they solve.Because do not want to take the space too long, so there is not too much source code analysis and grammar explanation, can be how simple simple.Redux First look at the Baidu encyclopedia above redux a picture: This is Redux'

1190000000684654What?PromiseIs CommonJS one of the specifications, the own,,,, and resolve reject done fail then so on, can help us control the flow of code, avoid multi-layered functions of nesting. Today, Async is becoming more and more important in web development, and for developers, this non-linear execution of programming can be difficult for developers to control, and allows Promise us to better control the code execution process, and jQuery so