0.0.2 • Public • Published

Koa Except

Bypass koa middleware under certain conditions.


npm i koa-except -S


With existing middlewares: You can add multiple exceptions using the and() method.

const jwt = require('koa-jwt')()
jwt.except = require('koa-except')
    .except({ method: 'POST', path: /\/auth$/ })
    .and({ path: /\/health$/ }))

Equivalently, you can pass multiple conditions as an array. To be technical, the array should be in Disjuntive Normal Form (DNF), where Objects act as conjunctions and Arrays act as clauses.

const jwt = require('koa-jwt')()
jwt.except = require('koa-except')
    { method: 'POST', path: /\/auth$/ },
    { path: /\/health$/ }

If you are authoring a middleware you can support except as follows:

module.exports = function () {
  function middleware (ctx, next) {
   // Do something
  middleware.except = require('koa-except')
  return middleware

Current options

  • opts: {Object|Array}
    • 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 either. 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 ctx.url instead of ctx.originalUrl.

koa-except returns a koa middleware function that also exposes an and(opts) method for chaining


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

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

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

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

Serve static files except when OPTIONS request is made

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


This library was directly inspired by Jesús Rodríguez who published koa-unless based on José F. Romaniello's implementation of the original express version.


MIT 2016 - Marlin Gingerich

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