......

3. Operation on file structure

3.1 fs.readdir(url,(error,data)=>{})

Role: Read all files in the folder
Reference: Path to url folder
Two parameters: callback function, built-in two parameters, error information and resource handle

const fs = require('fs');
//Asynchronous read mode
fs.readdir('./file',(error,data)=>{
	if(error):console.log('Failed to read folder');
	else{ console.log(data) } 
});

//Synchronized read with fewer callback functions and more return values
let data = fs.readdirSync('./file');
console.log(data);

3.2 fs.stat(url,(error,data)=>{});

Role: Read information about files and folders
Reference: path of url target file and folder;
Two parameters: callback function, built-in two parameters, error information and resource handle

const fs = require('fs');

//Read files/folders asynchronously
fs.stat('./file/aa',(error,data)=>{
	//Verify that it is a folder
	error?console.log('read failure'):console.log(data.isFile());
});

//Synchronous reading of files/folders has fewer callback functions and more return values than asynchronous reading
let result = fs.statSync('./file/aa');
console.log(result.isFile());//Boolean Value

Read files synchronously/Information in Folder size Property is the byte length of the file read

3.3 fs.mkdir(url,{recursive:true},error=>{})

Role: (Iteration) Create folders
Reference: Path created by url
Two parameters: {recursive:true} Whether to iterate creation
Three meals: Callback function built-in parameter, error message

//Introducing js core module - file management module fs
const fs = require('fs');

//Asynchronous Operation Create File
fs.mkdir('./file/aa/bb/cc',{recursive:true},error=>{
	error?console.log('Failed to create'):console.log('Created successfully');
});

//Synchronization Create File
fs.mkdirSync('./file/dd/ee/hh',{recursive:true});

3.4 fs.rmdir(url,{recursive:true},error=>{})

Role: (Iteration) Delete folder
Reference: Path to url deletion
Two parameters: {recursive:true} Whether to iteratively delete
Three meals: Callback function built-in parameter, error message

//Introducing core module fs
const fs = require('fs');

//Asynchronous operation to delete files
fs.rmdir('./file/aa',{recursive:true},error=>{
	error?console.log('Delete failed'):console.log('Delete succeeded');
});
//Synchronization Delete Files
fs.rmdirSync('./file/dd',{recursive:true});

3.5 fs.unlink(url + filename, error=>{})

Role: Delete files
Reference: Path + File Name
Two parameters: Callback function built-in parameter, error message

const fs = require('fs');
//Asynchronous operation to delete files
fs.unlink('./file/a.txt',error=>{
	error?console.log('Delete failed'):console.log('Delete succeeded')
});
//Synchronization Delete Files
fs.unlinkSync('./file/b.txt');

3.6 fs. Rename (original url + original file name, new url + new file name, error=>{})

Effect:
1. Move and rename the file by modifying both the url and the file name;
2. Moving files only changes url, not rename;
3. Rename the file without moving the url, just rename it;

Reference: original url + original file name;
Second parameter: new url + new file name;
Three parameters: Callback function has a built-in parameter, which is the error information;

const fs = require('fs');
//Asynchronous operations move files and rename them
fs.rename('./file/js.jpg','javaScript.jpg',error=>{
	error?console.log('Move and rename failed'):console.log('Move and rename successfully');
});
//Synchronization moves and renames
fs.renameSync('javaScript.jpg','./file/js.jpg');

3.7 Downloading a file reads the file and writes it to a new address file

fs.readFile('original url + file name', (error, resource handle) =>{
if(error){
console.log('Failed to read file');
}else{
//Write to file after successful reading
fs.writeFile('new url + file name', resource handle, {read method}, error=>{});
}; )

Role: Download the file, that is, read the file and write to the new address file

Reference: original url + original file name;
Two parameters: callback function, built-in two parameters, error information and resource handle date
Three parameters: new url + new file name;
Four parameters: resource handle data
Five parameters: reading method {flag:'w'}
Six parameters: Callback function has a built-in parameter, which is the error information;

Note: The suffix names must be the same when reading and downloading files.

const fs = require('fs');

//Read and write the same file asynchronously
fs.readFile('./file/js.jpg',(error,data)=>{
	if(error) console.log('read failure');
	else {
		//Write to file after successful reading
		fs.writeFile('javaScript.jpg',data,{flag:'w'},error=>{
			error?console.log('Write failed'):console.log('Download Successful');
		})
	}
})

4. Global approach

4.1 __dirname

Role: Get the absolute path of the folder where the file is located

console.log(__dirname);

4.2 __filename

Role: Get the absolute path to the location of the file

console.log(__filename);

(Temporarily updated at 2021.07.24 18:16 Please correct any errors...)