The difference between JS require and import

In JavaScript, we often use require and import to introduce modules or files. But many people are not clear about their differences. This article will introduce the difference between require and import in detail, and explain it in detail through code examples.

introduction

In modern JavaScript development, modularity has become a very important concept. Require and import are two commonly used methods of module introduction. Although they can both be used to introduce modules, there are some important differences between them that we need to understand in order to use them better.

The difference between require and import

1. Grammar

• require is the module introduction method of CommonJS, and the syntax is:const module = require('module')
• import is the ES6 module introduction method, and the syntax is:import module from 'module'

2. Dynamic loading

• require dynamically loads modules and can be used anywhere in the code
• import loads modules statically and can only be used at the top of the file

3. Export method

• require exports modules through module.exports
• import exports modules through export
  

Advantages and disadvantages of require and import

Both require and import in JS are keywords used to import modules, but they have some different advantages and disadvantages.

Advantages of require:

1. In Node.js, require is an import method of the CommonJS module system, which can be used directly on the server side without additional configuration.
2. require supports dynamic import and can import modules based on conditions at runtime.

Disadvantages of require:

1. require loads modules synchronously. When there are many modules or the modules are large, it will cause the performance of the application to decrease.
2. The require syntax is relatively old, does not support the ES6 module syntax, and cannot be used directly on the browser side.

Advantages of import:

1. Import is the import method of the ES6 module system, which supports asynchronous loading of modules and can improve application performance.
2. The import syntax is more concise and clear, supports named imports and default imports, and allows you to use modules more flexibly.

Disadvantages of import:

1. In Node.js, you need to use tools such as babel to convert ES6 module syntax to CommonJS syntax before it can be used.
2. import does not support dynamic import and cannot import modules at runtime based on conditions.

To sum up, require is suitable for Node.js environment and supports dynamic import, but its performance is poor; import is suitable for browser and Node.js environment and has better performance, but requires additional conversion tools and does not support dynamic import. According to the specific usage scenarios and needs, you can choose the appropriate import method.

Detailed code explanation

Example of using require to introduce a module

const fs = require('fs');
const path = require('path');

const filePath = path.join(__dirname, 'example.txt');
const content = fs.readFileSync(filePath, 'utf-8');
console.log(content);

Example of using import to introduce a module

import fs from 'fs';
import path from 'path';

const filePath = path.join(__dirname, 'example.txt');
const content = fs.readFileSync(filePath, 'utf-8');
console.log(content);

in conclusion

Through the introduction of this article, we understand the difference between require and import, and how to use them. In actual development, we should choose the appropriate introduction method according to the specific situation in order to better organize and manage our code.

I hope this article is helpful to everyone, thank you for reading!