前言

koa-router同时支持Koa1和Koa2,使用风格和Express相似，使用过Express的强烈推荐。

示例

app.js

const Koa = require('koa');
const app = new Koa();
const Router = require('koa-router');
const router = new Router();

router.use('/home', ...require('./home'));

// app.use(router.routes())
app.use(router.routes()).use(router.allowedMethods());

app.listen(3000);

home.js

const Router = require('koa-router');
const home = new Router();

// /home
home.get('/', async (ctx, next) => {
    ctx.response.status = 200;
    ctx.response.body = 'home';
    await next()
});
home.post('/list', async (ctx, next) => {
    ctx.response.status = 200;
    ctx.response.body = 'home-list';
    await next()
});

module.exports = [home.routes(), home.allowedMethods()];

router.allowedMethods()实现了什么?

其实查看一下源码就会发现，allowedMethods方法只是在ctx.status为404时，为响应头设置status和Allow而已。不添加也没有问题，返回404 Not Find.

附录

Router.prototype.allowedMethods = function (options) {
  options = options || {};
  var implemented = this.methods;

  return function allowedMethods(ctx, next) {
    return next().then(function() {
      var allowed = {};

      if (!ctx.status || ctx.status === 404) {
        for (var i = 0; i < ctx.matched.length; i++) {
          var route = ctx.matched[i];
          for (var j = 0; j < route.methods.length; j++) {
            var method = route.methods[j];
              allowed[method] = method
          }
        }

        var allowedArr = Object.keys(allowed);

        if (!~implemented.indexOf(ctx.method)) {
          if (options.throw) {
            var notImplementedThrowable;
            if (typeof options.notImplemented === 'function') {
              notImplementedThrowable = options.notImplemented(); // set whatever the user returns from their function
            } else {
              notImplementedThrowable = new HttpError.NotImplemented();
            }
            throw notImplementedThrowable;
          } else {
            ctx.status = 501;
            ctx.set('Allow', allowedArr.join(', '));
          }
        } else if (allowedArr.length) {
          if (ctx.method === 'OPTIONS') {
            ctx.status = 200;
            ctx.body = '';
            ctx.set('Allow', allowedArr.join(', '));
          } else if (!allowed[ctx.method]) {
            if (options.throw) {
              var notAllowedThrowable;
              if (typeof options.methodNotAllowed === 'function') {
                notAllowedThrowable = options.methodNotAllowed(); // set whatever the user returns from their function
              } else {
                notAllowedThrowable = new HttpError.MethodNotAllowed();
              }
              throw notAllowedThrowable;
            } else {
              ctx.status = 405;
              ctx.set('Allow', allowedArr.join(', '));
            }
          }
        }
      }
    });
  };
};