What are the benefits of nodejs modularity

Benefits of nodejs modularization: 1. Code decoupling can improve code reusability; 2. Code maintainability can be improved; 3. Code readability can be improved; 4. It can be implemented Load on demand; 5. Naming conflicts can be resolved; 6. Dependency management is convenient.

The operating environment of this tutorial: Windows 7 system, nodejs version 12.19.0, DELL G3 computer.

What is modularity?

In the field of programming, modularization is to follow fixed rules and split a large file into multiple small modules that are independent and interdependent. In layman's terms, a js file can Use data from another js file.

What are the benefits of modularity?

1. Code decoupling can improve the reusability of the code

2. It can improve the maintainability# of the code

##3. It can improve the

readability of the code.

4. It can realize

on-demand loading.

5. Can solve

naming conflicts

6. Convenient management of dependencies

The emergence of modularization also brings

module scope, which is similar to function scope , variables, methods, etc. defined in custom modules can only be accessed within the current scope. This access restriction effectively solves the problem of variable pollution.

Module specifications

Modular specifications are the rules that need to be followed when splitting and combining code into modules, such as:

• What syntax format is used to reference the module

• What syntax format is used in the module to expose members to the outside world

The benefits of modular specifications: everyone complies with the same modular specifications to write code, which reduces the cost of communication, greatly facilitates mutual calls between various modules, and benefits others and oneself

Module specification type:

• CommonJS Specification: The commonjs specification is followed in nodejs.

• ES6 Modular specification: (Modular specification common to front-end and back-end; can be used in Node.js, Vue, and React!)

• CMD and AMD Modular specifications (less used): CMD--sea.js, AMD-require.js

• UMD is called Universal Module Definition, which allows the same code module to run in projects using CommonJs, CMD or even AMD at runtime or compile time. It does not have its own proprietary specifications, but integrates the specifications of CommonJs, CMD, and AMD.

  Difference:
  1. For dependent modules, AMD is executed in advance, and CMD is executed delayed.
  2. CMD promotes dependencies nearby, while AMD promotes dependencies in the front.

nodejs module classification

##Built-in module --- fs (file system module).path( Path module).http (network operation module)...

• const fs = require("fs"); //node提供的基础模块,可以直接导入使用

Custom module --- .js file created by the user

• const m = require("./js文件名");//注意其中是相对路径,后缀名.js可加可不加

Third-party modules --- Modules developed by third-party individuals or teams, usually called

packages
• , need to be downloaded and imported before use

  const moment = require('moment');// 使用前需要通过npm i moment 命令安装该包

Import and export of modules

Import

Use the require() method to load modules

Note:

When using the require method to load other modules, the modules in the loaded module will be executed. Code

Export

There is a module object in each custom module, which

stores information related to the current module Information,
• One of the attributes exports can expose module members for external use. When loading a module, you get an empty object pointed to by the module.exports attribute.If you want to use this module For data in module.exports, you can add attribute values ​​to the module.exports property for external use.
• In order to simplify the code for sharing members externally, node provides the exports object.
By default, exports and module. exports points to the same object.

Note: When using the require() method to import a module, the import result will always be based on the object pointed to by module.exports

## Misunderstandings in the use of #exports and module.exports

exports = {
    username: 'ls',
    gender: '男'
}
module.exports = exports;
module.exports.age = '20';
// 导入后的结果为 {username:'ls',gender:'男',age:'20'}
 
exports = {
    username: 'ls',
    gender: '男'
}
module.exports.age = '20';
module.exports = exports;
// 导入后的结果为 {username:'ls',gender:'男'}
 
 
exports = {
    username: 'ls',
    gender: '男'
}
exports = module.exports;
module.exports.age = '20';
// 导入后的结果为 {age:'20'}

So try to use only one of the methods to avoid unnecessary troubleMore nodes For related knowledge, please visit:

nodejs tutorial

! !

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