Require.js usage method sharing

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1. Why use require.js

First of all, if a page loads multiple js files, the browser will stop rendering the web page. The more files are loaded, the web page will lose response time. will be longer; secondly, because there are dependencies between js files, the loading order must be strictly guaranteed. When the dependencies are complex, code writing and maintenance will become difficult.

require.js is to solve these two problems:

1. Implement asynchronous loading of js files to avoid web pages losing response;
2. Manage dependencies between modules , which facilitates code writing and maintenance.

2. Loading require.js

The first step is to download the latest version from the official website and load it directly on the page

<script src="js/require.js"></script>

Loading this file may cause the web page to be lost To respond, you can put it at the bottom of the page to load, or you can write the

<script src="js/require.js" defer async="true" ></script>

async attribute to indicate that this file needs to be loaded asynchronously to avoid the webpage losing response. IE does not support this attribute and only supports defer, so defer is also written.

After loading require.js, the next step is to load our own code, which is the entrance, which can be called the main module. If the file is named main.js, it can be written as follows:

<script src="js/require.js" data-main="js/main"></script>  .js后缀可以省略

3. How to write the main module

If the main module depends on jQuery, you can write it like this

require(['jquery'], function ($){ 
　　　alert($); 
});

4. require.config() method

require.config({ 
　　paths: { 
　　　　"jquery": "jquery.min", 
　　　　"underscore": "underscore.min", 
　　　　"backbone": "backbone.min"
　　} 
});

The above code The file names of the three modules are given, and the path defaults to the same directory as main.js (js subdirectory). If these modules are in other directories, such as the js/lib directory, there are two ways to write them.

• One is to specify the paths one by one

require.config({ 
　　paths: { 
　　　　"jquery": "lib/jquery.min", 
　　　　"underscore": "lib/underscore.min", 
　　　　"backbone": "lib/backbone.min"
　　} 
});

• The other is to directly change the base directory (baseUrl).

require.config({ 
　　baseUrl: "js/lib", 
　　paths: { 
　　　　"jquery": "jquery.min", 
　　　　"underscor: "underscore.min", 
　　　　"backbone": "backbone.min" 
　　} 
});

• If a module is on another host, you can also specify its URL directly, such as

require.config({ 
　　paths: { 
　　　　"jquery": "https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min"
　　} 
});

5. How to write AMD module

Modules loaded by require.js adopt AMD specifications. In other words, the module must be written according to AMD's regulations.

Specifically, the module must be defined using a specific define() function. If a module does not depend on other modules, it can be defined directly in the define() function.

// math.js 
define(function (){ 
　　var add = function (x,y){ 
　　　　return x+y; 
　　}; 
　　return { 
　　　　add: add 
　　}; 
});

The loading method is as follows:

 // main.js 
require(['math'], function (math){ 
　　alert(math.add(1,1)); 
});

If this module also depends on other modules, then the first parameter of the define() function must be an array to indicate the dependencies of the module sex.

define(['myLib'], function(myLib){ 
　　function foo(){ 
　　　　myLib.doSomething(); 
　　} 
　　return {  //返回模块中的函数 
　　　　foo : foo 
　　}; 
});

When the require() function loads the above module, the myLib.js file will be loaded first.

6. Loading non-standard modules (how to use shim)

// app.js 
 function sayHello(name){ 
 　alert('Hi '+name); 
}

// main.js 
require.config({ 
　　shim: { 
　　　　'app': { //这个键名为要载入的目标文件的文件名，不能随便命名。 
　　　　　　exports: 'sayHello' //exports的值为my.js提供的 对外接口的名称 
　　　　} 
　　} 
}); 
 
require(['app'], function(sayHello) { 
 alert(sayHello()) 
})

Exporting a function means that we get a javaScript class

But if in my.js There are many functions written in it. It is a bit troublesome to integrate them into one function. Want to export them directly? The method is as follows:

//　app.js 
function sayHi(name){ 
 alert('Hi '+name); 
} 
function sayHello(name){ 
 alert('Hiello '+name); 
}

// main.js 
　　require.config({ 
　　　　shim: { 
　　　　　　app: { 
　　　　　　　　init: function() { //这里使用init将2个接口返回 
　　　　　　　　　　return { 
　　　　　　　　　　　　sayHi: sayHi, 
　　　　　　　　　　　　sayHello: sayHello 
　　　　　　　　　　} 
　　　　　　　　} 
　　　　　　} 
　　　　} 
　　}); 
 
　　require(['app'], function(a) { 
　　　　a.sayHi('zhangsan'); 
　　　　a.sayHello('lisi'); 
　　});

Ordered import of shim

require.config({ 
 
 shim: { 
 　　 'jquery.ui.core': ['jquery'], //表示在jquery导入之后导入 
 　　 'jquery.ui.widget': ['jquery'], 
 　　 'jquery.ui.mouse': ['jquery'], 
 　　 'jquery.ui.slider':['jquery'] 
 　 }, 
 paths : {  
  jquery : 'jquery-2.1.1/jquery',  
  domReady : 'require-2.1.11/domReady',  
  'jquery.ui.core' : 'jquery-ui-1.10.4/development-bundle/ui/jquery.ui.core',  
  'jquery.ui.widget' : 'jquery-ui-1.10.4/development-bundle/ui/jquery.ui.widget',  
  'jquery.ui.mouse' : 'jquery-ui-1.10.4/development-bundle/ui/jquery.ui.mouse',  
  'jquery.ui.slider' : 'jquery-ui-1.10.4/development-bundle/ui/jquery.ui.slider' 
  } 
　　});  
 
　　require(['jquery', 'domReady','jquery.ui.core','jquery.ui.widget','jquery.ui.mouse','jquery.ui.slider'], function($) {    
 　　$("#slider" ).slider({    
 　　 value:0,   
 　　 min: 0,   
  　　max: 4,   
  　　step: 1,   
  　　slide: function( event, ui ) {}  
  　　 });  
　　 });

Related recommendations:

javascript advanced modular require.js Sharing examples of specific usage methods

Detailed explanation of specific methods of using advanced modular require.js in JavaScript

Summary of how to use Require.js

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