express跨域处理```js const express = require('express') const ap

const express = require('express')
const app = express()
app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*')
  res.header(
    'Access-Control-Allow-Headers',
    'Authorization,X-API-KEY, Origin, X-Requested-With, Content-Type, Accept, Access-Control-Request-Method'
  )
  res.header(
    'Access-Control-Allow-Methods',
    'GET, POST, OPTIONS, PATCH, PUT, DELETE'
  )
  res.header('Allow', 'GET, POST, PATCH, OPTIONS, PUT, DELETE')
  next()
})