asynchronous javascript tutorial

function as the second argument to promise's then method. Tips Promise represents the final value, which results when the parallel operation is completed Using promise to combine different parallel operations Use promise-mode APIs to avoid data contention Use Select (also known as choose) when required for intentional competitive conditions Extended reading Promise https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Refe

This article summarizes the 4 methods of "Asynchronous mode" programming, which allows you to write JavaScript programs that are more structured, better performing, and easier to maintain.first, the callback functionThis is the most basic method of asynchronous programming.Assume that there are two functions F1 and F2, which wait for the result of the former exec

function A () {var n = 0; for (var i=1;i Look at the above two functions, in the execution of the result of writing two input, it must be a function completed, and then execute the B function, this is a single thread queue. How to execute these two functions asynchronously, that is, a slow execution, and b do it directly without waiting for the end of a.# #setTimeout Mysterious function.This function is the key to Asynchrony, look at the code: Function C (fuc) {settimeout (function () {a (); f

Understanding jquery before implementing an asynchronous queue, it is necessary to understand the JavaScript asynchronous Pattern. JavaScript Async is not really a serious sense of asynchrony, JS makes certain fragments asynchronous way in the future, the stream does not hav

At the outset, it is somewhat difficult to understand the order of the asynchronous program's invocation. For example, in the following program, starting will be printed first, then finished:downloadasync ( " file.txt" , function (file ) { Console.log ( " Finished );}); Console.log ( " Starting ); downloadasync method returns immediately after execution, and it simply registers a callback function for downloading this behavior. Because of the

JavaScript has a large number of asynchronous operations. First, you can see what in JS will generate Asynchronization (Here we only consider the situation in the browser ): Ajax (XMLHttpRequest) Image Tag, Script Tag, iframe (similar principle) SetTimeout/setInterval CSS3 Transition/Animation PostMessage Web Workers Web Sockets And more... In fact, in my own understanding, anything that "occurs i

); } }, 1); return this; } By using settimeout, we ensure that the actual operation of the yield is done asynchronously. We then update the results of the user's incoming yield and the related state to the object properties, and then traverse Callbackqueue to invoke all the callback functions. Summary So we do a simple JavaScript asynchronous invocation framework, the complete code can loo

Ajax|javascript| Request | asynchronous Most WEB applications use the request/response model to obtain complete HTML pages from the server. Often click on a button, wait for the server to respond, and then click another button, and then wait, such a repetitive process. With Ajax and XMLHttpRequest objects, you can use a request/response model that eliminates the need for the user to wait for a response from

execution, and the asynchronous mechanism is implemented by the browser, by the browser's two or more resident threads to do together, and the main task or JS single-threaded to implement the worker thread just another open up a task queue This task queue will store all the results of asynchronous method execution, and when the main thread stack of JS is fully executed, it will go to the task queue to find

: " +Error);} Downloadasync ( "a.txt" ,function(Error,a) {if(Error) {OnError(error);return; } downloadasync ( "b.txt" ,function(Error,b) { // duplicated error-checking logic if(Error) {OnError(error);return; } downloadasync (Url3,function(Error,C) { // duplicated error-checking logic if(Error) {OnError(error);return; } Console. Log( "Contents: " +A+B+c); }); });});To increase the readability of the code, many developers omit the braces for the IF statement block that is us

The following code, how long will the ' end ' pop up? Why? The code is as follows Copy Code var t = true;settimeout (function () {t = false;}, 1000);while (t) {}Alert (' End '); This is an implementation that was previously thought of when you could not implement a blocking JavaScript thread (that is, to implement the Sleep method).It's simple, isn't it?Is it? Re-recognize