Modular
- The built-in module does not need to be installed, the external module needs to be installed;
this file is a custom module
require("./home");//The same level directory of the custom module needs to be added./
The file name built-in module of the following file
require("tt"); //Store in node_modules and execute according to the rules of built-in modules.
npm package manager (alias: module manager)
npm common commands:
- npm init: guide to create a package.json file
- npm root to view the path of the current package installation or through npm root -g to view the global installation path;
- npm -v view version
- node -v node version book
- npm i jquery --save
- npm i cookie client
- npm i axios --save-dev
npm i axios --save-dev This is the development dependency
"dependencies" in package.json : {//Run dependency
"jquery": "^3.6.0" //npm i jquery --save
},
"devDependencies": {}, //Development dependencies
npm install module_name -S or --save means npm install module_name --save write dependencies
npm install module_name -D or --save-dev means npm install module_name --save-dev write devDependencies
fs module
- fs is a file operation module. All file operations are divided into synchronous and asynchronous. The characteristic is that synchronization will add "Sync", such as: asynchronous read file "readFile", synchronous read file "readFileSync";
A preliminary understanding of the fs module
//fs:操作文件的模块 内置模块
const fs = require("fs");
> 增删改查
1. 文件操作 2. 目录操作
1. File operation
- Write file
writeFile(): Write file
Parameter 1: File name, including file format
Parameter 2: File, the content to be written
fs.writeFile("1.txt", "我是需要写入的文件", function(err) {
if (err) {
return console.log(err); //输出报错信息
}
console.log("写入成功");
});
When the written file exists, the original file content will be overwritten and
{flag:"a"}
parameters will also be {flag:"a"} parameter 3. Configuration object {}: flag attribute: a is appended write
w: write (default value)
r: Read
fs.writeFile("1.txt", "我是追加进来的内容", {
flag: "w" }, function(err) {
if (err) {
return console.log(err); //输出报错信息
}
console.log("写入成功");
});
File read fs.readFile
冷门方式
fs.readFile("1.txt",(err,data)=>{
if(err){
return console.log(err);
}
console.log(data.toString());
})
fs.readFile():
回调函数中 参数1：错误的信息
"utf-8"
fs.readFile("1.txt", "utf-8", (err, data) => {
if (err) {
return console.log(err);
}
console.log(data);
})
所有的文件操作，默认都有同步和异步；
默认是同步的，需要异步的话，在方法名前加Sync
例如：readFileSync();
fs.readFileSync("1.txt", "utf-8");
console.log(data);
// let data = fs.readFileSync("1.xtx").toString();
// console.log(data);
/Change file name: Rename
//Parameter 1: Original file name
//Parameter 2: New file name
fs.rename("1.txt", "11.txt", err => {
if (err) {
return console.log(err);
}
console.log("修改成功");
});
Delete file – fs.unlink("")
fs.unlink("2.txt", err => {
if (err) {
return console.log(err);
}
console.log("删除成功");
})
Copy files
fs.copyFile();
1.本质是先读取，再写入
fs.copyFile("11.txt", "aa.txt", err => {
if (err) {
return console.log(err);
}
console.log("复制成功");
})
2.封装复制
function myCopyFile(src, dest) {
fs.writeFileSync(dest, fs.readFileSync(src));
}
myCopyFile("11.txt", "4.txt");
2: Directory operation
No suffix format is required when manipulating directories
创建目录
fs.mkdir("ding", err => {
if (err) {
return console.log(err);
}
console.log("创建成功");
})
修改目录名称
fs.rename("ding", "da", err => {
if (err) {
return console.log(err);
}
console.log("修改成功");
})
读取目录
fs.readdir("da", (err, data) => {
if (err) {
return console.log(err);
}
console.log(data);//读出来的是一个数组
})
删除目录(空目录/空文件夹)
fs.rmdir("da", err => {
if (err) {
return console.log(err);
}
console.log("删除成功");
})
判断文件或目录是否存在
fs.exists("5.txt", function(exists) {
console.log(exists); //是否找到指定内容 找到就是true找不到就是false
})
//获取文件或目录的详细信息
fs.stat("http.html", (err, data) => {
if (err) {
return console.log(err);
}
console.log(data);
// //Is it a file
// let res = data.isFile();
// console.log(res);
// //Is it a directory
// data.isDirectory();
})
Delete non-empty directories
Ideas: 1. Delete the files in the directory first.
2. When you know that the directory is empty, delete the directory directly
function removerDir(path) {
//获取目录
let data = fs.readdirSync(path);
//["a",2.html","3.txt","4.txt"]
// console.log(data)
//总体思路
for (let i = 0; i < data.length; i++) {
//循环判断目录中的每一个内容
//处理子目录的路径
let url = path + "/" + data[i];
/*
循环1： url = "22/a"
循环2：下来就是a文件 然后时a文件下面的所有内容
*/
//获取详细信息
let stat = fs.statSync(url);
console.log(stat.isDirectory());
if (stat.isDirectory()) {
//如果是目录 继续查找
removerDir(url);
} else {
//文件，删除
fs.unlinkSync(url); // path = 22
}
}
//当循环结束后，目录成为空目录
fs.rmdirSync(path);
}
//注意事项：在使用node.js删除文件时，不会经过回收站
// 在删除前， 切记备份
// 一面删除错误，发生不可挽救的损失
removerDir("22");
Pay special attention to these two places
The buffer of buffer buffer data is also a class, not a module
- The way it is created now
- Parameters: is the size of the content, in bytes
let buffer = Buffer.alloc(10); console.log(buffer);
- Buffer will convert the data to binary and then display it in hexadecimal format
let buffer = Buffer.from(“大家好”); console.log(buffer);
let buffer1 = Buffer.from([0xe5, 0xa4, 0xa7, 0xe5, 0xae, 0xb6, 0xe5, 0xa5, 0xbd]);
这里要注意的是上面的参数要以这种0xe5， 才会转换为字符串
console.log(buffer1); <Buffer e5 a4 a7 e5 ae b6 e5 a5 bd>
console.log(buffer1.toString())大家好
let buffer2 = Buffer.from("大家好");
console.log(buffer2)
/字符串创建
//StringDecoder: 固定名称
let {
StringDecoder } = require("string_decoder");
let decoder = new StringDecoder();
let res1 = decoder.write(buffer1);
let res2 = decoder.write(buffer2);
console.log(res1 + res2);
stream
- Stream: Stream and data processing are inseparable
//stream 流
const fs = require("fs");
//读取了数据
let rs = fs.createReadStream("11.txt");
//将数据写入
let ws = fs.createReadStream("aa.txt");
//管道
rs.pipe(ws);
console.log(rs);
//流 ，会把数据分成64kb的小文件传输
let num = 0;
let str = "";
//数据传输时，触发的方法
rs.on("data", chunk => {
console.log(chunk);
num++;
str += chunk;
console.log(chunk);
console.log(num)
})
//数据传递完成后
rs.on("end", () => {
console.log(str)
})