04 基础 API

Review

  1. 2023/02/16
  2. 2023-02-25 16:23
  3. 2024-08-15

一、Introduction #

二、重要API #

  1. __filename 当前脚本文件路径. The __filename in Node returns the filename of the executed code. It gives the absolute path of the code file.
  2. __dirname 当前脚本文件夹路径. The __dirname in a node script returns the path of the folder where the current JavaScript file resides. It gives the absolute path of the code file.
  3. process.cwd() The process.cwd() method returns the current working directory of the Node.js process

setTimeout setInterval setImmediate

process

  1. argv
  2. env
  3. stdin
  4. stdout
  5. exit
process.stdin.on('data', e => {

})

Paths #

const path = require('node:path');

const notes = '/users/joe/notes.txt';

path.dirname(notes); // /users/joe
path.basename(notes); // notes.txt
path.extname(notes); // .txt

path.basename(notes, path.extname(notes)); // notes, get the file name without the extension by specifying a second argument to `basename`
  • dirname: gets the parent folder of a file
  • basename: gets the filename part
  • extname: gets the file extension

path.resolve vs path.join vs path.normalize

  1. path.resolve creates the absolute path of a relative path. The method creates absolute path from right to left until an absolute path is constructed.

For example:

path.resolve('joe.txt'); // '/Users/joe/joe.txt' if run from my home folder
path.resolve('tmp', 'joe.txt'); // '/Users/joe/tmp/joe.txt' if run from my home folder
path.resolve('/etc', 'joe.txt'); // '/etc/joe.txt'

path.resolve('/a', 'b', 'c');     //    C:\a\b\c
path.resolve('/a', '/b', 'c');    //    C:\b\c
path.resolve('/a', '/b', '/c');   //    C:\c

If absolute path is not generated, the method using current working directory:

path.resolve('a', 'b', 'c');     //    C:\{current_working_directory}\a\b\c
  1. path.join joins all path and the normalize the result For example:
const name = 'joe';
path.join('/', 'users', name, 'notes.txt'); // '/users/joe/notes.txt'
path.join('/a', '/b', '/c');   //   /a/b/c
path.join('/a', '/b', 'c');    //   \a\b\c
path.join('/a', 'b', 'c');     //   \a\b\c
path.join('a', 'b', 'c');      //   a\b\c
  1. path.normalize() is another useful function, that will try and calculate the actual path, when it contains relative specifiers like . or .., or double slashes:
path.normalize('/users/joe/..//test.txt'); // '/users/test.txt'

path.relative(from, to) The path.relative() method returns the relative path from from to to based on the current working directory. If from and to each resolve to the same path (after calling path.resolve() on each), a zero-length string is returned.

If a zero-length string is passed as from or to, the current working directory will be used instead of the zero-length strings.

path.relative('/data/orandea/test/aaa', '/data/orandea/impl/bbb');
// Returns: '../../impl/bbb'

path.isAbsolute(path)

  • path.format(pathObject) => String
  • path.parse(path) => Object, returns an object whose properties represent significant elements of the path.

path.delimiter Provides the platform-specific path delimiter:

  • ; for Windows
  • : for POSIX

FS Module #

File System or fs module is a built in module in Node that enables interacting with the file system using JavaScript.

  • fs.appendFile() The fs.appendFile() method appends specified content to a file. If the file does not exist, the file will be created:
  • fs.open()
  • fs.writeFile() The fs.writeFile() method replaces the specified file and content if it exists. If the file does not exist, a new file, containing the specified content, will be created.

The fs.open() method takes a “flag” as the second argument, if the flag is “w” for “writing”, the specified file is opened for writing. If the file does not exist, an empty file is created:

var fs = require('fs');  

fs.open('mynewfile2.txt', 'w', function (err, file) {  
  if (err) throw err;  
  console.log('Saved!');  
});
var fs = require('fs');  
  
fs.appendFile('mynewfile1.txt', ' This is my text.', function (err) {  
  if (err) throw err;  
  console.log('Updated!');  
})

To delete a file with the File System module,  use the fs.unlink() method. To rename a file with the File System module,  use the fs.rename() method.

  1. fs-extra https://github.com/jprichardson/node-fs-extra
  2. globby https://github.com/sindresorhus/globby
  3. glob https://github.com/isaacs/node-glob
  4. chokidar https://github.com/paulmillr/chokidar

Chokidar Node.js fs.watch:

  • Doesn’t report filenames on MacOS.
  • Doesn’t report events at all when using editors like Sublime on MacOS.
  • Often reports events twice.
  • Emits most changes as rename.
  • Does not provide an easy way to recursively watch file trees.
  • Does not support recursive watching on Linux.

Node.js fs.watchFile:

  • Almost as bad at event handling.
  • Also does not provide any recursive watching.
  • Results in high CPU utilization.

Chokidar resolves these problems.

Reference #

https://nodejs.org/en/learn/manipulating-files/nodejs-file-paths https://nodejs.org/api/path.html https://nodejs.org/api/fs.html https://www.w3schools.com/nodejs/nodejs_filesystem.asp