promise in node js

The new standard adds to native promise. This is just a case of chained use, think about the details. One, review of then () and catch ()Then () and catch () parameters can be placed in the callback function to receive the final result of a promise.Then () can receive a parameter, then this callback will only be called when Promise Resolve ().Then () can also receive the second parameter, then the second ca

First, describeWe know that the JavaScript implementation environment is "single-threaded", so-called single-threaded, is only able to perform one task at a time, if there are multiple tasks to queue, the previous task is completed before you can continue the next task.This "single-threaded" advantage is simple to implement, easy to operate, the disadvantage is that it is prone to blocking, because if a task in the queue time is longer, then the subsequent tasks can not be executed quickly, or c

* */Callbacks Fs.readfile ('./promise-1.js ',' UTF8 ',function(Err, Content1) {Nesting onceConsole.log (' # ', Content1) fs.readfile ('./promise-1.js ',' UTF8 ',function (err, Content2) {//second nesting console.log ( ' # # ', Content2)}) }) //promises readfileasync (function (content1) {console.log ( ' # ', content1)

no new state changes are Made. therefore, There are only two final results for the Promise Object.the asynchronous Operation succeeds, the Promise object returns a value, and the state becomes Resolved. the asynchronous Operation failed, and the Promise object throws an error and the state becomes Rejected. 3. The generation of the

Recently has been studying JS promise object, which has a blog written relatively easy to understand, forwarded as follows:Http://www.cnblogs.com/lvdabao/p/es6-promise-1.htmlReferring to the described above, I wrote the test example, understand the use of promise, and then wrote a FS

This article mainly introduces a simple node. js server example. This article implements a simple helloworld example and shows how to run this server, for more information, see the following example: hello world. It seems that the first section of each language tutorial will talk about this, and we are no exception. First, create a project directory, which can be defined by yourself. In this case, the d

background: Hybridapp, the front end uses Js-bridge method to call native interface, such as acquiring device information, taking pictures, face recognition and so on. The front end encapsulates the call library, and each time the native interface is called, two steps are required (1, mount the native callback function under window, 2, call the Invokenative function, send the request data) before transformation:With callbacks, you mu

This article mainly introduces several important knowledge points of node. js: The Role of node. js, callback, synchronous and asynchronous code, event loop 1, and the role of node. js, The meaning of I/O. Move the mouse to see t

Asynchronous programming practices of when. js under node. js, node. jswhen. js Assume a business scenario: Get and save the rss feed to a file through the rss address, and save the rss address to the file. To complete the business in this scenario, you need to complete thre

This article mainly introduces the asynchronous programming practices of when. js under node. js. If you need it, you can refer to the following assumptions for a business scenario: Get and save the rss feed to a file through the rss address, and save the rss address to the file. To complete the business in this scenario, you need to complete three tasks: 1. Rea

ES6 in promise can be said to improve the asynchronous callback nesting problem, then if we write a library like promise how should we write?Let's take a look at the features of promise:　　第一：Promise构造函数接受一个函数作为参数，函数里面有两个参数resolve和reject分别作为执行成功或者执行失败的函数var promise=New Proms

Why is Node. js so popular? Why is Node. js popular? Why is node. js popular? Node. js is a server technology used to build and run Web appl

model change correctly$scope. $apply (function() {deferred.notify ('About to greet' +name+ '.'); if(Oktogreet (name)) {Deferred.resolve ('Hello,' +name+ '!'); } Else{deferred.reject ('Greeting' +name+ 'is not allowed.'); } }); }, +); returndeferred.promise; } varPromise=Asyncgreet ('Robin Hood'); Promise.then (function(greeting) {Console.info ('Success:' +greeting); }, function(reason) {Console.info ('Failed:' +reason); }, function(update) {Console.info ('Got Notification: