Analysis of JS modularity

This article mainly introduces the analysis of JS modularization, which has certain reference value. Now I share it with everyone. Friends in need can refer to it

1. Understanding

1. What are modules and modularization?

Encapsulate a complex program into several files according to certain specifications and combine them together

2. Why modularize?

Reduce complexity, improve decoupling, and facilitate deployment

3. Benefits of modularization

• Avoid naming conflicts (reduce namespace pollution)

• Better separation, on-demand loading

• Higher reusability

• High maintainability

4. Page introduction loading script

2. Modular specification

1, CommonJS (node ​​is written according to this specification)

Instructions:

Every file can be As a module

On the server side: the module is loaded synchronously during runtime

On the browser side: the module needs to be compiled and packaged in advance Processing

Basic syntax:

Module introduction: require(xxx)

Third-party module: xxx is the module name

Custom module: xxx is the module file path

Exposed module: exports.xxx = value and module.exports = value

The essence of the exposed module is the exports object

Exports itself is an empty object exports.xxx = value is to add attributes or methods to the exports object

Module.exports = value is to directly overwrite the original empty object with the new value object

Implementation:

Server-side implementation: Node .js

Browser-side implementation: Browserify (CommonJS browser-side packaging tool)

Download and install browserify

Global: npm install browserify -g

Local: npm install browserify --save-dev

Define module code ( js file code and expose the corresponding content)

Introduce the module Use require to introduce the module in app.js but the browser does not recognize the require method and needs to package and process js

In the terminal in the root directory, enter browserify js/src/app.js -o js/dist/bundle.js (js/src/app.js source file js/dist/bundle.js is the packaged output file )

Page usage introduction:

(What the browser actually runs is the file generated by the package)

2. AMD

Instructions:

is specially used Due to the modularization specification on the browser side, module loading is asynchronous

Basic syntax:

Define exposed modules:

　//定义没有依赖的模块：
　　define(function(){
　　　　return 模块
　　})
　　//定义有依赖的模块：
　　define(['module1','module2'],function(m1,m2){
　　　　return 模块
　　})

Introduce the use module:

require(['module1','module2'],function(m1,m2){
　　　　使用m1/m2
　　})

Implementation (browser side):

Require.js

3. CMD (understand)

Instructions: Specifically used on the browser side, the loading of the module is asynchronous, and the module will be loaded and executed only when it is used

Basic syntax:

Define exposed module:

　//定义没有依赖的模块：
　　define(function(require,exports,module){
　　　　exports.xxx = value
　　　　module.exports = value
　　})
　　//定义有依赖的模块：
　　define(function(require,exports,module){
　　　　//引入依赖模块(同步)
　　　　var module2 = require("./module2")
　　　　//引入依赖模块（异步）
　　　　require.async("./module3",function(m3){
　　　　})
　　　　//暴露模块
　　　　exports.xxx = value
　　})

Introduce using module:

require(function(require){
　　　　var m1 = require('./module1')
　　　　var m4 = require('./module4')
　　　　m1.show()
　　　　m4.show()
　　})

Implementation (browser side): Sea.js

4, ES6

Note: Dependent modules need to be compiled and packaged

Syntax:

Export module: export xxx

Import module: import xxx from "url"

Page introduction

Implementation (browser side):

Use Babel to compile ES6 to ES5 code

Using Browserify to compile and package js

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