What is modularity in nodejs

In nodejs, modularization refers to splitting a large file into multiple small modules that are independent and interdependent. Each js file is considered a separate module; the modules are invisible to each other. If a module needs to use another module, it needs to use the specified syntax to introduce the module, and only the content exposed by the module can be imported. The syntax is "const variable name = require('module path');".

The operating environment of this article: Windows 10 system, nodejs version 12.19.0, Dell G3 computer.

What is modularity in nodejs

Concept

Background: In team collaboration, different members will independently write the code they are responsible for, such as A Responsible for a.js, B is responsible for b.js. If a.js and b.js define the same variable, when using the two files, an error will be reported if the variable has the same name. That is, global variable pollution. Solution ->nodejs modularization

Concept: Modularization in nodejs means that each js file will be considered a separate module. Modules are invisible to each other. If a module needs to use another module, it needs to import the module to be used by specifying the syntax, and only the content exposed by the imported module can be used.

Modularization is to follow fixed rules and split a large file into multiple small modules that are independent and interdependent. In layman's terms, one js file can use the data in another js file.

Syntax: including introduction and exposure

Introduction module

const 变量名 = require('模块的路径');

Exposure syntax (choose 1 from the following 2 syntaxes)

Internal module:

1、多次暴露
module.exports.属性名1 = 数据1;
module.exports.属性名2= 数据2;
2、一次性暴露完
module.exports ={
    属性名1:数据1,
    属性名:2数据2,
}

Module path details

• ./:Current directory

• ../:The directory above the current directory

• ./Next level directory/

• You can omit the .js suffix when introducing modules

• When introducing the nodejs own module or the package downloaded by npm, you do not need to write the path, directly write the module name

1、引入上一级目录下的a.js模块
let 变量名= require('./../a');
2、引入下一级目录routes下的b.js模块
let 变量名= require('./routes/b');
3、引入npm下载的jQuery模块
let 变量名= require('jquery');

Extended knowledge:

Modularization has What are the benefits?

1. It can improve the reusability of the code

2. It can improve the maintainability of the code

3. It can achieve on-demand loading (when learning vue It will be very obvious)

The emergence of modularization also brings about module scope, which is similar to function scope. Variables, methods, etc. defined in a custom module can only be accessed within the current scope. This This kind of access restriction effectively solves the problem of variable pollution.

Recommended learning: "nodejs video tutorial"

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