promise chaining

I learned about async and promise a long time ago, but always smattering.Today, when writing Nodejs, found a lot of third-party libraries using callbacks, so in the actual operation will appear multiple callbacks, this is the legendary JS callback hell.As an example,There is a way to call Redis, access a hash object table, get the return value, and insert the return value into the other hash object table of Redis.Testcallbackaction () {Let Redis = red

Here is a summary of the usage and description of Q in Node. js, without introducing promise and Principles.* Promise is to solve the JS in the callback hierarchy too deep code difficult to understand the problem of Change.Q is one of the promise packages implemented in nodejs, which is a common library in Nodejs.How to install Q in your project:NPM Install Q-sav

A normal function is encapsulated into a promise instance, there are 3 key steps, the first step is to construct a promise instance inside the function, the second step is to complete the execution of the deployment function to change the state of promise, and the third step is to return the promise instance. Each

JQuery's show and hide methods are well known and know that it can accept a callback function for execution after the animation completes. Like what: $ ('. Js-sam '). Hide (' slow ', function () {Alert (' You just hid Sam ');}); However, the JQuery 1.8 version also provides another writing style, namely promise– this Chinese translation is very difficult, now see there is a promise-I still continue to use

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 promise example, the code is as fol

encapsulating Ajax and Promise First, Ajax Ajax is called "Asynchronous JavaScript and XML" (Asynchronous JavaScript and XML) refers to the development of interactive Web applications to create a technology, improve the user experience, achieve no refresh effect. Advantages:A, no plug-in support requiredb, the page does not refresh, the use of asynchronous way to communicate with the server, with more rapid response capabilities, excellent user expe

20060325 This topic is a bit out of fashion, but I just remembered that I did not see the promise before I saw the blood of Shantou, and I was not interested in watching the promise. I would not have liked Chen Kaige's film. When the promise was raging across China, I was also indifferent. I only knew that there was a

What is promiseThere are many asynchronous implementations in JavaScript, delay functions, callback functions, and ES6 new generator functions, where promise is also one of the ways to implement Asynchrony.About the asynchronous implementation of JavaScript in detail and the difference, the post-update blog, please look forward to, no longer repeat here.$Q ServicesIn short $q service is a promise implementa

is worth noting that when the deferred state is switched (called reject or resolve later), and then the callback function is bound, then the corresponding state of the callback function will be executed immediately.As an example:Deferred can also return its own subset of operations.promiseThere is only one API that binds the callback, and no stateful switching API.deferred: reject, resolve, done, fail, then, alwaysPromise: Done , fail, then, alwaysis obviously

Copyright NOTICE: This work is licensed under the Creative Commons Attribution-NonCommercial use-Share 4.0 International license agreement in the same way. Reprint please indicate source Http://blog.csdn.net/azureterniteDirectory (?) [+]The concept of promise The Promise object is used for asynchronous (asynchronous) computations: A Promise object repres

Promise is to solve the callback! There's a guy called Q in the NPM package that specializes in encapsulating promise to solve callback problems. About promise Introduction and Q's introductory point here. Here's how to use Q to encapsulate an API that only provides a callback function as a Promise mode: (Take the off

The most recent way to implement mock virtual data through node is to use the FS module of node to read and write to our local files to achieve a mock function: We can develop a JS file that specializes in encapsulating a simple file-reading function. The JS code is as follows: Let FS = require (' FS '); Let DEALFN = {/** * [write Data via promise] * @param {String} file [FileName] * @param {object} obj [written data (object)] * @return {Object}