javascript - What does synchronous vs asynchronous loading mean? - Stack Overflow

admin管理员组

文章数量:1352184

Reading from this site, I understand that using monjs means that when the browser finishes downloading your files, it will have to load them up 1 by 1 as they depend on each other. But with AMD, it can load multiple ones at the same time so that even if file a depends on file b, it part of file a can be executed before file b is finished?

CommonJS Modules: The dominant implementation of this standard is in Node.js (Node.js modules have a few features that go beyond CommonJS). Characteristics: Compact syntax Designed for synchronous loading and servers

Asynchronous Module Definition (AMD): The most popular implementation of this standard is RequireJS. Characteristics: Slightly more plicated syntax, enabling AMD to work without eval() (or a pilation step) Designed for asynchronous loading and browsers

Reading from this site, I understand that using monjs means that when the browser finishes downloading your files, it will have to load them up 1 by 1 as they depend on each other. But with AMD, it can load multiple ones at the same time so that even if file a depends on file b, it part of file a can be executed before file b is finished?

CommonJS Modules: The dominant implementation of this standard is in Node.js (Node.js modules have a few features that go beyond CommonJS). Characteristics: Compact syntax Designed for synchronous loading and servers

Asynchronous Module Definition (AMD): The most popular implementation of this standard is RequireJS. Characteristics: Slightly more plicated syntax, enabling AMD to work without eval() (or a pilation step) Designed for asynchronous loading and browsers

• javascript
• node.js
• asynchronous
• amd
• monjs

Share Improve this question Follow asked Nov 17, 2017 at 6:53 stackjleistackjlei 10k1919 gold badges7373 silver badges124124 bronze badges

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 6

Synchronous programming is executing code line by line. Same with loading. It will load 1 by 1 whatever that you are loading. Real world example: You are in a queue in cinema for a movie ticket. Asynchronous would be many people in restaurant. You order food and other people order food. They dont need to wait for your order to finish. Everyone can order but you dont know when the order will e. Same as with loading. You can load multiple things at the same time or different intervals but it doesnt guarantee that it will e in that order. I hope the explanation is good enough.

The syntax with CommonJS in loading modules is as such:

var MyModule = require("MyModule");

As you can see, this will block the thread until the module is downloaded, from either your filesystem or the web. This is called synchronous loading. This is impossible to achieve in a normal web browser environment without affecting user experience, since we cannot block the thread as the browser uses the thread to update the graphics.

With RequireJS, it's done as such:

// In your module
define(["dependencies", ...], function(){
    return MyModule;
})

// In your web page
require(["dependencies", ...], function(MyModules, ...){
    // do stuff here
});

With this model, our web page does not depend on the timing of when the module should be loaded. We can load our scripts in parallel while the page is still being loaded. This is called asynchronous loading. Once the scripts are loaded, they will call define which notifies RequireJS that the scripts are indeed loaded and executed. RequireJS will then call your main function and pass in the initialized modules.

本文标签： javascriptWhat does synchronous vs asynchronous loading meanStack Overflow