后端代码

• 这里使用koa-body获取post请求的数据

• koa-body可以处理三种类型的请求
  • multipart/form-data
  • application/x-www-urlencoded
  • application/json

const Koa = require('koa')const app = new Koa()const koaBody = require('koa-body')app.use(koaBody())app.use(ctx => {  ctx.set('Access-Control-Allow-Origin', `*`)  console.log('type', ctx.request.type)  console.log(ctx.request.body)  ctx.body = `Request Body: ${
     JSON.stringify(ctx.request.body)}`})app.listen(3000)复制代码

• 这样写在前端浏览器中请求会报错，需要再加上

ctx.set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");复制代码

前端代码

/* jquery默认的content-type是application/x-www-form-urlencoded，当content-type是application/json时需要把参数转换为json字符串*/$.ajax({ type:'post', url:'http://localhost:3000', contentType: "application/json",data:JSON.stringify({ a:123}), success:res=>{   console.log(res); }, error:err=>{   console.log(err) }})/* axios默认的content-type是application/json，当content-type是x-www-form-urlencoded时需要把参数转换为字符串传递如`a=1&b=2`*/axios.post('http://localhost:3000', {   firstName: 'Fred',   lastName: 'Flintstone' }) .then(function (response) {   console.log(response) }) .catch(function (error) {   console.log(error) }) /*fetch  默认的content-type是 text/plain, 当content-type是x-www-form-urlencoded时需要把参数转换为字符串传递如`a=1&b=2`, 当content-type是application/json时需要把参数转换为json字符串 */fetch('http://localhost:3000', { method: 'POST', headers: {   'Content-Type': 'application/json' }, body: JSON.stringify({   name: 'Hubot',   login: 'hubot', })}).then(res=>{ console.log(res);})复制代码