A middleware is a mechanism you can add to the server, doing some work on each request.

This can be inside a plugin, but also directly written into Admin > Options > Server code.

A middleware has the form of a function that receives a Context object as a parameter. The context object contains all information about the http request and the http response.

Basic examples

Setting http header

exports.middleware = ctx => ctx.set('x-my-header', 'some value')

Custom reply to some address

exports.middleware = ctx => {
  if (ctx.path === '/some/address')
    ctx.body = 'my content'
}

Allow only Chrome as browser

exports.middleware = ctx => ctx.get('user-agent').includes('Chrome') || ctx.socket.destroy()