This is a JS function to record keyboard input and process callback for specific key combinations. If you see a problem or know how to make it better, please contact me.

keyCodeCallback.js

function getEventCode(event) {
  if (event.key !== undefined) {
    return event.key;
  }
  if (event.keyIdentifier !== undefined) {
    return event.keyIdentifier;
  }
  if (event.keyCode !== undefined) {
    return event.keyCode;
  }
  return undefined;
}

function setupKeyCodeHandler() {
  if (window.keyStack === undefined) {
    window.keyStack = new Map();
    window.keyStack.callbacks = new Map();
    window.keyStack.on = function(command, callback) {
      if (typeof command !== "string" || typeof callback !== "function") {
        throw new Error("The first parameter must be a string and the second must be a callback");
      }
      var cbs = window.keyStack.callbacks.get(command);
      if (cbs === undefined) {
        cbs = [];
      }
      cbs.push(callback);
      window.keyStack.callbacks.set(command, cbs);
    };
    window.keyStack.check = function() {
      propagate = true;
      window.keyStack.callbacks.forEach((cbs, command) => {
        var commands = command.split(" ");
        var execute = 0;
        for (let c of commands) {
          if (window.keyStack.get(c)) {
            execute++;
          }
        }
        if (commands.length > 0 && execute === commands.length) {
          for (let cb of cbs) {
            propagate = propagate && cb();
          }
        }
      });
      return propagate;
    };
    document.onkeyup = function(e) {
      keyCode = getEventCode(e);
      if (keyCode === undefined) {
        return true;
      }
      window.keyStack.set(keyCode.toLowerCase(), false);
      return window.keyStack.check();
    };
    document.onkeydown = function(e) {
      keyCode = getEventCode(e);
      if (keyCode === undefined) {
        return true;
      }
      window.keyStack.set(keyCode.toLowerCase(), true);
      return window.keyStack.check();
    };
    return true;
  }
  return false;
}


//Usage
setupKeyCodeHandler(); //setup keyCodeHandler, returns true if ok, returns false if already set
window.keyStack.on('control e', () => {
  console.log("Ctrl + E");
  return false;//key combinations that are used by the browser must return false to prevent default browser action
});