Conditionally skip a middleware when a condition is met.

npm i koa-unless --save

With existing middlewares:

var unless = require('koa-unless');
var serve  = require('koa-static');
var static = serve(__dirname + '/public');
static.unless = unless;
app.use(static.unless({ method: 'OPTIONS' }));

If you are authoring a middleware you can support unless as follow:

module.exports = function () {
  var mymid = function *(next) {
	// Do something
  };
  mymid.unless = require('koa-unless');
  return mymid;
};

• method it could be an string or an array of strings. If the request method match the middleware will not run.
• path it could be an string, a regexp or an array of any of those. If the request path match, the middleware will not run.
• ext it could be an string or an array of strings. If the request path ends with one of these extensions the middleware will not run.
• custom it must be a function that returns true / false. If the function returns true for the given request, ithe middleware will not run. The function will have access to Koa's context via this
• useOriginalUrl it should be true or false, default is true. if false, path will match against this.url instead of this.originalUrl.

Require authentication for every request unless the path is index.html.

app.use(requiresAuth.unless({ path: ['/index.html', '/'] }))

Avoid a fstat for request to routes doesnt end with a given extension.

app.use(static.unless(function () {
  var ext = url.parse(this.originalUrl).pathname.substr(-4);
  return !~['.jpg', '.html', '.css', '.js'].indexOf(ext);
}));

All the credits for this library goes for José F. Romaniello which created the original express version.

MIT 2015 - Jesús Rodríguez