koa-cors

编写 Cors 中间件

---

const maxAge = 6000;
const credentials = true;
const methods = "GET,HEAD,PUT,POST,DELETE";
const whiteList = ["http://localhost:3001"];
const exposeHeaders = "a,b,c";

function Cors() {
  return async (ctx, next) => {
    const {
      method,
      header: { origin, referer },
    } = ctx.request;
    const source = origin || referer;
    if (!whiteList.includes(source)) {
      ctx.status = 401;
      ctx.set("WWW-Authenticate", "Basic");
      ctx.body = "非法域名";
      return;
    }
    ctx.set("Access-Control-Max-Age", maxAge);
    ctx.set("Access-Control-Allow-Origin", source);
    ctx.set("Access-Control-Allow-Methods", methods);
    ctx.set("Access-Control-Expose-Headers", exposeHeaders);
    credentials && ctx.set("Access-Control-Allow-Credentials", "true");
    ctx.set(
      "Access-Control-Allow-Headers",
      ctx.get("access-control-request-headers")
    );
    if (method === "OPTIONS") {
      ctx.status = 204;
      ctx.body = "OPTIONS 预检请求";
      return;
    }
    await next();
  };
}

module.exports = Cors;

使用 Cors 中间件

---

const Cors = require("./middlewares/cors");
app.use(Cors());