An article explaining in detail how to read and write files in Nodejs

How to operate files in

Node? The following article will talk about how to use Nodejs to read and write files. I hope it will be helpful to you!

# Manipulating files is a basic function of the server and one of the necessary capabilities for back-end development.

Operating files mainly includes reading and writing. These functionsNodejshave already provided corresponding methods. Just call it.

Create folder

Synchronization method

const fs = require('fs') fs.mkdirSync(`${__dirname}/雷猴`)

NodeJSThere is a file module calledfs. To operate on files, this module must be introduced first.

Use thefs.mkdirSyncmethod to create a folder. Just enter the name of the folder to be created.

__dirnamerefers to the absolute path of the folder where the current file is located.

Asynchronous creation

const fs = require('fs') fs.mkdir(`${__dirname}/雷猴`, err => { if (err) { console.error(err) } })

Use thefs.mkdirmethod to create asynchronously. The first parameter is also the folder name, and the second is Back to the function, there is aerrparameter in this function, which can return error information.

Delete files

After creating the folder, I originally wanted to talk about "delete the folder". However, since all the files in the folder must be cleared before deleting it, the usage ofDeleting fileswill be discussed first.

There are two ways to delete files:synchronousandasynchronous.

Synchronization fs.unlinkSync

const fs = require('fs') fs.unlinkSync(`${__dirname}/test.txt`);

fs.unlinkSyncInput the path and file name of the file to be deleted to delete the specified file.

Asynchronous fs.unlink

const fs = require('fs') fs.unlink(`${__dirname}/test.txt`, err => { if (err) { console.error(err) } })

fs.unlinkThe method has 2 parameters. The first parameter is the file path and file name. The second parameter is the callback function that monitors deletion failure.

Delete Folder

Before deleting a folder, clear all files in the target folder.Files can be deleted usingfs.unlinkSyncorfs.unlink.

Sync

const fs = require('fs') fs.rmdirSync(`${__dirname}/雷猴`)

Asynchronous

const fs = require('fs') fs.rmdir(`${__dirname}/雷猴`, err => { if (err) { console.error(err) } })

The usage is similar to deleting files. There are also synchronous and asynchronous methods for deleting folders. , accepts 2 parameters asynchronously, and the second parameter is also a callback for monitoring error reports.

Write data

const fs = require('fs') const content = ' 雷猴雷猴\n' const opt = { flag: 'a', // a：追加写入；w：覆盖写入 } fs.writeFile('test.txt', content, opt, (err) => { if (err) { console.error(err) } })

fs.writeFilemethod can write content to a file. If the file does not exist, it will be automatically created.

fs.writeFileParameter description:

• First parameter: file name
• Second parameter: written content
• The third parameter: writing mode (append, overwrite, etc.)
• The fourth parameter: error message monitoring

Reading data

const fs = require('fs') fs.readFile('fileName', (err, data) => { if (err) { console.error(err) return } // data 是二进制类型，需要转换成字符串 console.log(data.toString()) })

Use thefs.readFilemethod to read data. The first parameter is the file name; the second parameter is the callback,errmonitors error messages,datais the data read back.

It should be noted that thedataread back is a binary type of data, which needs to be converted into data we can understand using thetoString()method.

Check whether the file exists

const fs = require('fs') const exist = fs.existsSync('fileName') console.log(exist)

Use thefs.existsSyncmethod to check whether the specified file exists, and returntrue# if it exists. ## ; Otherwise, returnfalse.

Summary

If you use

NodeJSas the backend, you cannot escape the knowledge of reading and writing files. Its most common function can write logs, such as collecting error logs, etc.

We can also write logs in the database, but not all computers have the same database installed. But if you write the log in a file, the contents of the file can generally be easily opened on other computers.

For more node-related knowledge, please visit:

nodejs tutorial!

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