Koa2 中間件

koa文檔

程序理解圖

1：根目錄創建文件夾

 mkdir middleware

2：新建

 touch middleware/koa-pv.js

3：內容

function pv(ctx) {
    global.console.log(ctx.path)
}

module.exports = function () {
    return async function (ctx, next) {
        pv(ctx)
        await next()
    }
}

4：引入app.js

const pv = require('./middleware/koa-pv')
app.use(pv())

成功

5：多個樣例
新建 m1

function m1(ctx) {
    global.console.log('m1')
}

module.exports = function () {
    return async function (ctx, next) {
        global.console.log('m1 start')
        m1(ctx)
        await next()
        global.console.log('m1 end')
    }
}

新建m2

function m2(ctx) {
    global.console.log('m2')
}

module.exports = function () {
    return async function (ctx, next) {
        global.console.log('m2 start')
        m2(ctx)
        await next()
        global.console.log('m2 end')
    }
}

新建m3

function m3(ctx) {
    global.console.log('m3')
}

module.exports = function () {
    return async function (ctx, next) {
        global.console.log('m3 start')
        m3(ctx)
        await next()
        global.console.log('m3 end')
    }
}

引入

const m1 = require('./middleware/m1')
const m2 = require('./middleware/m2')
const m3 = require('./middleware/m3')

app.use(m1())
app.use(m2())
app.use(m3())

運行結果