How to set up nodejs module

Node.js is a JavaScript runtime environment based on the Chrome V8 engine, which can help us build and run efficient web applications. The core idea of ​​Node.js is modularization, which means encapsulating a function or code block in an independent module that can be referenced and reused in other modules. In this article, we will explore how to set up modules in Node.js.

1. Create a module

In Node.js, each JavaScript file is a module, and a module can contain several variables, functions, objects, etc. Variables, functions, etc. defined in a module can only be used within the module and must be exported when using other modules.

The following is an example module named example.js:

const sayHello = name => {
  console.log(`Hello, ${name}!`);
};

module.exports = {
  sayHello,
};

This module defines a function named sayHello, and Export it so that other modules can use it.

2. Import module

In Node.js, to import a module, you need to use the require function, which can pass in the path of the module , returns an object, the content of the object is the variables, functions, etc. exported by the module.

const example = require('./example.js');

example.sayHello('Tom');

In the above code, first use the require function to import the example.js module. After importing, we can call the function exported by the modulesayHello, and pass in a parameter Tom.

3. Export module content

After using module.exports to export variables, functions, etc., other modules can use require The function references the module, but variables, functions, etc. defined in the module will not be exported by default. If you want to export a variable or function, you can assign it to the module.exports object or add it to the object.

const name = 'Tom';

const sayHello = () => {
  console.log(`Hello, ${name}!`);
};

module.exports = {
  name,
  sayHello,
};

In the above code, we exported the variable name and the function sayHello. These two variables can be referenced or called in other modules.

4. Using third-party modules

In Node.js, there are a large number of third-party modules available, you can use the npm command line tool Download and install these modules. After installation, you can import third-party modules just like your own modules by specifying their names.

For example, to install and use the lodash library:

const _ = require('lodash');

const arr = [1, 3, 2, 4, 2];

const uniqArr = _.uniq(arr);

console.log(uniqArr); // [1, 3, 2, 4]

In the above code, we first installed ## using the npm command line tool #lodash, then imported the module through the require function, and finally used the function uniq in the module to deduplicate the array arr.

Summary

In this article, we introduced how to set up modules in Node.js, including creating modules, importing modules, exporting module contents, and using third-party modules. Proper use of modularization can improve code reuse and reduce maintenance costs.

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