1. 创建文件mockService.js
2. 打开控制台 node mockService.js
3. 在network中可以查看到。
   （我写的vue+mock初级入门中不可在network中查看到请求）

let express = require("express"); //引入express模块
let Mock = require("mockjs"); //引入mock模块
let app = express(); //实例化

/*post方法*/
var bodyParser = require("body-parser"); 
app.use(bodyParser.json()); // 添加json解析
app.use(
  bodyParser.urlencoded({
    extended: false
  })
);

/*为app添加中间件处理跨域请求*/
app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Methods", "PUT, GET, POST, DELETE, OPTIONS");
  res.header("Access-Control-Allow-Headers", "X-Requested-With");
  res.header("Access-Control-Allow-Headers", "Content-Type");
  next();
});
app.get("/api/demo", function(req, res) {
  res.json(
    Mock.mock({
      status: 200,
      "data|3": [
        {
          "value|+1": 1,
          "label|+1": ["demo1", "demo2", "demo3"]
        }
      ]
    })
  );
});
//post请求需要引入上面所标注的
app.post("/api/trains", function(req, res) {
  console.log(req.body);
  res.send({ status: 200, msg: "success" });
});
app.listen("5000", function() {
  console.log("app listening at http://localhost:5000");
});