node后端与Vue前端跨域处理方法详解

const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors')
const expressJWT = require('express-jwt')
const app = express();
const users = require('./routes/users')
const config = require('./config')
app.use(expressJWT({secret: config.jwtSecretKey}).unless({path: [/^\/api\/users/]}))
// const db = require('./db/index')
app.use(cors())
app.use(express.urlencoded({extended: false}))
app.use(bodyParser.json())
app.get('/', (req, res) => {
    res.send('hello world !')
})
app.use('/api/users', users)
const testRouter = require('./routes/testToken')
app.use('/my', testRouter)
const profiles = require('./routes/profiles')
app.use('/api/profiles', profiles)
app.use((err, req, res, next) => {
    if (err) return res.send({status: 400, message: err})
    if(err.name === 'UnauthorizedError') return res.send({status: 404, message: '身份认证失败'})
    res.send({status: 404, message: err})
})
app.listen(5000, () => {
    console.log('api server running at http://127.0.0.1:5000')
})

const cors = require('cors')
app.use(cors())

import Vue from 'vue'
import App from './App.vue'
import ElementUI from 'element-ui';
import 'element-ui/lib/theme-chalk/index.css';
import router from './router'
import axios from './http'
Vue.use(ElementUI);
axios.defaults.baseURL = 'http://127.0.0.1:5000/api/'
Vue.prototype.$axios = axios;
Vue.config.productionTip = false
new Vue({
  router,
  render: h => h(App),
}).$mount('#app')

import axios from "axios";
import { Message, Loading } from 'element-ui';
let loading;
function startLoading(){
    loading = Loading.service({
        lock: true,
        text: '数据加载中',
        background: 'rgba(0,0,0,0.7)'
    })
}
function endLoading(){
    loading.close();
}
// 请求拦截
axios.interceptors.request.use(config => {
    startLoading();
    return config
}, error => {
    return Promise.reject(error)
})
//响应拦截
axios.interceptors.response.use(response => {
    endLoading();
    return response
}, error => {
    endLoading();
    Message.error(error.response.data)
    return Promise.reject(error)
})
export default axios

  methods: {
    submitForm(formName) {
      this.$refs[formName].validate(valid => {
        if (valid) {
          this.$axios
            .post("/users/register", this.registerUser)
            .then(res => {
              // 注册成功
              this.$message({
                message: "注册成功！",
                type: "success"
              });
              // this.$router.push("/login");
            });
        } else {
          console.log("error submit!!");
          return false;
        }
      });
    }
  }