A small utility to generate MIDI messages for testing purposes. It's an web app that works in all browsers that support Web MIDI.
Online here: https://hisschemoller.github.io/midi-tester/
WebMidi.js library is used for handling MIDI.
Source: https://github.com/djipco/webmidi
Documentation: http://djipco.github.io/webmidi/latest/classes/WebMidi.html