Introduction to CommonJs and custom modules in NodeJs

This article brings you an introduction to CommonJs of NodeJs and custom modules in NodeJs. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Custom modules in CommonJs and NodeJs

1. What is CommonJs

Balabala said a lot in the tutorial, my understanding That is, CommonJs is the standard of modularity, and NodeJs is the implementation of CommonJs (modularity). Applications written with the CommonJS API can not only use JavaScript to develop client applications, but also write the following applications:
a. Server-side JavaScript applications (nodejs)
b. Command line tools
c. Desktop graphical interface application

2. Modularization in NodeJs

Node applications are composed of modules and adopt the CommonJs module specification.

In Node, modules are divided into two categories:

One type is the module provided by Node, called the core module; the other type is the module written by the user, called the file module.
The core module part is in Node During the compilation process of the source code, a binary executable file is compiled. In Node When the process starts, some core modules are directly loaded into the memory. Therefore, when this part of the core module is introduced, the two steps of file location and compilation and execution can be omitted, and priority is determined in the path analysis, so its loading speed is fastest. For example: HTTP module, URL module, and Fs module are all nodejs Built-in core modules. Can be imported and used directly.
The file module is dynamically loaded at runtime, requiring complete path analysis, file location, compilation and execution process. The speed is slightly slower than the core module, but it is used a lot. These modules need to be defined by ourselves. Next, let's take a look at the custom modules in nodejs.

Provisions for custom modules in CommonJS (Nodejs)

We can extract the public functions into a separate js file as a module. By default, the methods or attributes in this module are as follows: , inaccessible from the outside. If you want the outside world to access the methods or properties in the module, you must expose the properties or methods in the module through exports or module.exports.
In the files that need to use these modules, introduce this module through require. At this time, you can use the properties and methods exposed in the module.
Here I made a picture for easy understanding:

• ##Definition of using modules

Create two new js

##3. npm init generates package.json

npm init -yes

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