想實現(xiàn)前端發(fā)送注冊的賬號密碼數(shù)據(jù)通過Post請求給后臺，但是后臺該咋寫啊。我一點注冊，它就提示報錯說“Cannot POST /”這是我的vue.js前端代碼register(){            if(this.username == ''|| this.password == ''){                 alert('請輸入用戶名或密碼')             }else{                 let data = {'username':this.username,'password':this.password}                this.$axios.post('/register/qian',data)                 .then((res)=>{                     console.log(res)                    this.$router.push('register')                 })                              }         }這是node.js后臺的，用了express 和 mongooserouter.post('/register/qian',function(req,res){req.on('data',function(data){     obj=JSON.parse(data)    console.log(obj)     res.send('數(shù)據(jù)已接受') })})