axioskoa-开发小记

Access to XMLHttpRequest at ‘http://localhost:8888/’ from origin ‘http://localhost:8080’ has been blocked by CORS policy: Request header field content-type is not allowed by Access-Control-Allow-Headers in preflight response.

axios 如果携带着 data 参数发送请求，会添加一个自定义请求头：Access-Control-Request-Headers: content-type，在发送正式请求前会发送 OPTIONS 预检请求，如果后端没有对应的设置响应头，将无法通过而报出以上错误。

解决方法：

server.use(async (ctx, next) => {console.log(`visited PATH: ${chalk.blue(ctx.path)}`)
  ctx.set({
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Headers': 'Content-Type'
  })
  await next()})

后端放行这个请求头