const Koa = require("koa")
const route = require("koa-route")
const app = new Koa()
app.use(async function middleware1(ctx, next) {
console.log("middleware1 ")
await next()
console.log("middleware1 ")
})
app.use(async function middleware2(ctx, next) {
console.log("middleware2 ")
await next()
console.log("middleware2 ")
})
app.use(async function middleware3(ctx, next) {
console.log("middleware3 ")
await next()
console.log("middleware3 ")
})
app.use(route.get("/", (ctx, next) => {
ctx.body = "hello koa"
}))
app.listen(3001, function () {
console.log("server is listening on port 3001")
})
middleware1
middleware2
middleware3
middleware3
middleware2
middleware1 this code uses Koa, to follow Koa"s "onion ring" middleware model, and the code in the middleware executes like a "paper clip" with the result as above.
const express = require("express")
const app = express()
app.use(function middleware1(req, res, next) {
console.log("middleware1 ")
next()
console.log("middleware1 ")
})
app.use(function middleware2(req, res, next) {
console.log("middleware2 ")
next()
console.log("middleware2 ")
})
app.use(function middleware3(req, res, next) {
console.log("middleware3 ")
next()
console.log("middleware3 ")
})
app.get("/", function (req, res, next) {
res.end("hello express")
})
app.listen(3000, function () {
console.log("server listening on port 3000!")
})
middleware1
middleware2
middleware3
middleware3
middleware2
middleware1 Express is linear, and the code after next () should not be executed, but the execution result of the above code is the same as using Koa.
I would like to ask the bosses to explain why the implementation result is like this.