koa笔记一（Context）

Koa将Node的request 和 response对象都封装到了context中，每次请求都会创建一个ctx，并且在中间件中作为接收器使用。

let ctx = {
    // 请求
    request: {
        method: 'GET',
        url: '/',
        // request header
        header: {
            host: '127.0.0.1:3030',
            connection: 'keep-alive',
            'cache-control': 'max-age=0',
            'upgrade-insecure-requests': '1',
            'user-agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.67 Safari/537.36',
            accept: 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8',
            'accept-encoding': 'gzip, deflate, br',
            'accept-language': 'zh-CN,zh;q=0.9,en;q=0.8',
            cookie: 'connect.sid=s%3AnQtQApNcQ55RmpjnkmQvWNTrdjYhZnlh.1FQUbVqpwpdRj8N6wjv8nOarf8hyzIpcxXN2LPYXGy0'
        }
    },
    // 响应
    response: {
         status: 200, 
         message: 'ok', 
         header: { 
            'content-type': 'text/plain; charset=utf-8',
            'content-length': '9'
        }
    },
    app: { 
        subdomainOffset: 2, 
        proxy: false, 
        env: 'development' 
    },
    originalUrl: '/',
    // 原生Node的request对象
    req: '<original node req>',
    // 原生Node的reponse对象
    res: '<original node res>',
    socket: '<original node socket>'
}