How to get files in nodejs

Node.js is a javascript running environment based on the Chrome V8 engine, which can run javascript code on the server side. In Node.js, how to obtain files is a relatively basic question. This article will discuss the following aspects:

1. Introduction to the fs module
2. API of the fs module
3. Application scenarios of the fs module

1. Introduction to the fs module

In Node.js, to operate files, you need to use the fs module. The fs module provides a series of operations such as reading, writing, copying, and renaming files. The fs module can be used to operate the local file system.

To use the fs module, you need to introduce the module in the code. The usage method is as follows:

const fs = require('fs')

2. API of the fs module

1. fs.readFile()

This method is used to read the file content asynchronously. The syntax is as follows:

fs.readFile(path[, options], callback)

Among them, path is the file path; options is the read option, and the encoding format can be passed in, such as utf-8, etc.; callback is the callback function, used to return the file content.

Example:

fs.readFile('./test.txt', 'utf-8', (err, data) => {
    if(err) {
        console.error(err)
    }else{
        console.log(data)
    }
})

In this example, read the test.txt file, read its content in utf-8 encoding format, and finally print out the read content in the callback function .

2. fs.readFileSync()

This method is used to read the file content synchronously. The syntax is as follows:

fs.readFileSync(path[, options])

Among them, path is the file path to be read; options is the reading option, and the encoding format can be passed in, such as utf-8, etc.

Example:

const data = fs.readFileSync('./test.txt', 'utf-8')
console.log(data)

In this example, the test.txt file is read synchronously, its content is read in utf-8 encoding format, and the read content is finally printed out.

3. fs.writeFile()

This method is used to write the file content asynchronously. The syntax is as follows:

fs.writeFile(file, data[, options], callback)

Among them, file is the file path to be written; data is the content to be written; options is the writing option, and the encoding format can be passed in, such as utf-8, etc.; callback is the callback function , used to return the writing result.

Example:

fs.writeFile('./test.txt', 'Hello Node.js!', 'utf-8', (err) => {
    if(err) {
        console.error(err)
    }else{
        console.log('写入成功！')
    }
})

In this example, write the string with the content of "Hello Node.js!" into the test.txt file, and print "Write" after the writing is successful. success!".

4. fs.writeFileSync()

This method is used to write the file content synchronously. The syntax is as follows:

fs.writeFileSync(file, data[, options])

Among them, file is the file path to be written; data is the content to be written; options is the writing option, and the encoding format can be passed in, such as utf-8, etc.

Example:

fs.writeFileSync('./test.txt', 'Hello Node.js!', 'utf-8')
console.log('写入成功！')

In this example, the string with the content of "Hello Node.js!" is synchronously written into the test.txt file, and "write" is printed after the writing is successful. Enter success!".

5. fs.readdir()

This method is used to asynchronously obtain a list of all files and subdirectories in the specified directory. The syntax is as follows:

fs.readdir(path[, options], callback)

Among them, path is the directory path to obtain the file list; options is the read option; callback is the callback function used to return the obtained file list.

Example:

fs.readdir('./', (err, files) => {
    if(err) {
        console.error(err)
    }else{
        console.log(files)
    }
})

In this example, obtain the list of all files and subdirectories in the current directory, and print out the obtained list in the callback function.

3. Application scenarios of fs module

In actual development, there are many application scenarios of fs module. Here are a few common application scenarios:

1. Read Write local files: Use fs.readFile(), fs.writeFile() and other methods to realize the function of reading and writing local files.
2. Get directory list information: Use the fs.readdir() method to obtain file and subdirectory list information in the specified directory.
3. Create and delete directories: Use fs.mkdir(), fs.rmdir() and other methods to create and delete local directories.
4. Read and write local pictures: Use fs.readFile(), fs.writeFile() and other methods to realize the function of reading and writing local pictures.

Summary:

This article introduces the main methods and application scenarios of obtaining files in Node.js. The fs module is the core module for operating local file systems in Node.js. Mastering the basic operations of the fs module is essential for Node.js developers.

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