Node的API基础

fs

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

// fs的异步方式
fs.readFile('./file.txt', 'utf-8', (err, data) => {
    if (err) throw err
    console.log(data, '异步')
})

// fs的Promise的链式调用
const { promisify } = require('util');
const readFile = promisify(fs.readFile);
readFile('./file.txt', 'utf-8').then(function (data) {
    console.log(data, 'Promise');
}).catch(function (err) {
    console.error('读取文件失败');
});

// fs的Promise的链式调用
const fsp = fs.promises;
fsp.readFile('./file.txt', 'utf-8').then(data => {
    console.log(data, 'fs.promises异步')
});

buffer

// 创建一个长度为10字节以0填充的Buffer
const buf1 = Buffer.alloc(10)
console.log(buf1)

// 创建一个Buffer包含ascii.
const buf2 = Buffer.from('a')
console.log(buf2)

// 创建Buffer包含UTF-8字节
const buf3 = Buffer.from('中文')
console.log(buf3)

// 合并Buffer
const buf4 = Buffer.concat([buf2, buf3])
console.log(buf4)

http

const http = require('http')
const fs = require('fs')
const server = http.createServer((request, response) => {
    // response.end('hello ...')
    const { url, method, headers } = request
    if (url === '/' && method === 'GET') {
        // 静态页面服务
        fs.readFile('index.html', (err, data) => {
            if (err) {
                // 500
                response.writeHead(500)
                response.end('500 Page err')
                return
            }
            response.statusCode = 200
            response.setHeader('Content-Type', 'text/html')
            response.end(data)
        })
    } else if (url === '/users' && method === 'GET') {
        // Ajax服务
        response.writeHead(200, {
            'Content-Type': 'application/json'
        })
        response.end(JSON.stringify({
            name: 'laowang'
        }))
    } else if (method === 'GET' && headers.accept.indexOf('image/*') !== -1) {
        // 图片文件服务
        fs.createReadStream('./' + url).pipe(response)
    } else {
        // 404
        response.writeHead(404)
        response.end('404 Page Not Found')
    }
})
server.listen(3000)

stream

//二进制友好，图片操作
const fs = require('fs')
const rs = fs.createReadStream('./img.png')
const ws = fs.createWriteStream('./img2.png')
rs.pipe(ws)