koa是如何解决跨域的？

cors设置跨域头,通过中间件的方式调用。

httpCors.js

const httpCors = async (ctx, next) => { ctx.set('Access-Control-Allow-Origin', '*'); ctx.set('Access-Control-Allow-Headers', 'Content-Type, Content-Length, Authorization, Accept, X-Requested-With , yourHeaderFeild'); ctx.set('Access-Control-Allow-Methods', 'PUT, POST, GET, DELETE, OPTIONS'); if (ctx.method == 'OPTIONS') {  ctx.body = 200;  } else { await next(); } }; module.exports = httpCors;

app.js

app.use(httpCors)