中间件

mid.js

const app = {
    callback (ctx) {
        console.log(ctx)
    },

    use (fn) {
        app.middleware = app.middleware || []
        app.middleware.push(fn)
    },

    go (ctx) {
        app.middleware = app.middleware || []
        var func = app.middleware.reverse().reduce(function(preMiddle, nextMiddle) {
            return function() {
                return nextMiddle(ctx, preMiddle)
            }
        }, function() {
            return app.callback(ctx)
        })
        func()
    }
}

app.use((ctx, next) => {
  ctx.name = 'Lucy'
  next()
})

app.use((ctx, next) => {
  ctx.age = 12
  next()
})

app.use((ctx, next) => {
  console.log(`${ctx.name} is ${ctx.age} years old.`) // => Lucy is 12 years old.
  next()
})

app.go({})