index.js

var keynameOf = require("keyname-of");
var events = require("dom-event");

module.exports = on;
module.exports.on = on;
module.exports.off = off;

function on (element, keys, callback) {
  var expected = parse(keys);

  var fn = events.on(element, 'keyup', function(event){

    if ((event.ctrlKey || undefined) == expected.ctrl &&
       (event.altKey || undefined) == expected.alt &&
       (event.shiftKey || undefined) == expected.shift &&
       keynameOf(event.keyCode) == expected.key){

      callback(event);
    }

  });


  callback['cb-' + keys] = fn;

  return callback;
}

function off (element, keys, callback) {
  events.off(element, 'keyup', callback['cb-' + keys]);
}

function parse (keys){
  var result = {};
  keys = keys.split(/[^\w]+/);

  var i = keys.length, name;
  while ( i -- ){
    name = keys[i].trim();

    if(name == 'ctrl') {
      result.ctrl = true;
      continue;
    }

    if(name == 'alt') {
      result.alt = true;
      continue;
    }

    if(name == 'shift') {
      result.shift = true;
      continue;
    }

    result.key = name.trim();
  }

  return result;
}