how to make a middleware based on koa, which is used for Intercept HTTP response?

Question

My project base on koa,I want to intercept HTTP response,when the response's message is "no promission",then excute 'this.redirect()'.

Answer 1

Your middleware (interceptor in my example) can access the response body after it yield next, so just place your logic after it yields.

var route = require('koa-route');
var app = require('koa')();

var interceptor = function*(next) {
  // wait for downstream middleware/handlers to execute 
  // so that we can inspect the response

  yield next; 

  // our handler has run and set the response body,
  // so now we can access it

  console.log('Response body:', this.body);

  if (this.body === 'no promission') {
    this.redirect('/somewhere');
  }
};

app.use(interceptor);

app.use(route.get('/', function*() {
  this.body = 'no promission';
}));

app.listen(3001, function() {
  console.log('Listening on 3001...');
});