ASCII Control Codes Keyboard Input Helper for Firefox

This is a script to help inputting ASCII Control Codes such as TAB, CR, LF, etc. on Firefox web browsers using ALT+Numpad keys. Inputted control codes must begin with 0 (e.g. 09, 013, etc.), and only control code 1 to 31 are accepted.

As of 11. 09. 2017. See the latest version.

You will need to install an extension such as Tampermonkey, Greasemonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Userscripts to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install a user script manager extension to install this script.

(I already have a user script manager, let me install it!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(I already have a user style manager, let me install it!)

// ==UserScript==
// @name         ASCII Control Codes Keyboard Input Helper for Firefox
// @namespace    ASCIIControlCodesKeyboardInputHelperForFirefox
// @version      1.0.1
// @description  This is a script to help inputting ASCII Control Codes such as TAB, CR, LF, etc. on Firefox web browsers using ALT+Numpad keys. Inputted control codes must begin with 0 (e.g. 09, 013, etc.), and only control code 1 to 31 are accepted.
// @author       jcunews
// @include      *://*/*
// @grant        none
// @run-at       document-start
// ==/UserScript==

var numpadKeyCodes = [45, 35, 40, 34, 37, 12, 39, 36, 38, 33]; //Insert, End, Down, PgDn, Left, Clear, Right, Home, Up, PgUp
var code = "";

function numFromKeyCode(keyCode) {
  if ((keyCode >= 96) && (keyCode <= 105)) { //Numpad0 - Numpad9
    return keyCode - 96;
  } else return numpadKeyCodes.indexOf(keyCode);
}

function keyUp(ev, ele, cc, i, s) {
  ele = document.activeElement;
  if ((ele.tagName === "TEXTAREA") || ((ele.tagName === "INPUT") && (ele.type === "text"))) {
    ev = ev || window.event;
    if (ev.altKey) {
      cc = numFromKeyCode(ev.keyCode);
      if (cc >= 0) code += cc;
    } else {
      if ((ev.keyCode === 18 /*ALT*/) && (code.charAt(0) === "0") && (code = parseInt(code, 10)) && (code < 32)) {
        i = ele.selectionStart;
        s = ele.value;
        ele.value = s.substring(0, i) + String.fromCharCode(code) + s.substring(ele.selectionEnd, s.length);
        ele.selectionEnd = i + 1;
      }
      code = "";
    }
  } else code = "";
}

if (window.InstallTrigger) document.addEventListener("keyup", keyUp);