A javascript regex to allow only Latin characters and other helpful keys

Question

For an HTML input value, is it possible to define with JavaScript a regular expression that accepts only Latin characters (any case) and all other keys like backspace, delete, arrow keys, and also .dot, @at? Is it for event key evaluation, not afterwards, that's why I need the arrow and the other keys.

Answer 1

You can use something like:

JavaScript

document.getElementById('foo').onkeydown = function (e) {
  if (e.keyCode < 65 || e.keyCode > 90) {
    e.preventDefault();
    return false;
  }
};

HTML

<textarea id="foo"></textarea>

This will limit you to enter only small letters. It should be a little modified to work also with uppers.

JSfiddle .

Answer 2

Unless you give more details, I think regex will not help you.

I don't know details of the key event you need to use, but I wrote myself a object like a dictionary, worked well in one of my projects, but of course its not fail proof, and it's very hard to be 100%, because of many keyboard layout and languages out there, and the unstandadized event handling in javascript and browsers implementations. I suggest reading first this article it helped me a lot http://unixpapa.com/js/key.html

My workaround for en-US english keyboards.

var Keys = { "BACKSPACE":8, "TAB":9,"ENTER":13,"SHIFT":16,"CTRL":17,"ALT":18, "PAUSEBREAK":19, "CAPSLOCK":20,"ESC":27, "SPACE":32, "PAGEUP":33, "PAGEDOWN":34, "END":35, "HOME":36, "LEFT":37, "UP":38, "RIGHT":39, "DOWN":40, "PRNTSCRN":44, "INSERT":45, "DELETE":46, "0":48, "1":49, "2":50, "3":51, "4":52, "5":53, "6":54, "7":55, "8":56, "9":57, "A":65, "B":66, "C":67, "D":68, "E":69, "F":70, "G":71, "H":72, "I":73, "J":74, "K":75, "L":76, "M":77, "N":78, "O":79, "P":80, "Q":81, "R":82, "S":83, "T":84, "U":85, "V":86, "W":87, "X":88, "Y":89, "Z":90, "WINKEY":91, "WINKEYR":92, "APPLICATION":93, "NUM0":96, "NUM1":97, "NUM2":98, "NUM3":99, "NUM4":100, "NUM5":101, "NUM6":102, "NUM7":103, "NUM8":104, "NUM9":105, "MULTIPLY":106, "ADD":107, "SUBTRACT":109, "DECIMALPOINT":110, "DIVIDE":111, "F1":112, "F2":113, "F3":114, "f4":115, "F5":116, "F6":117, "F7":118, "F8":119, "F9":120, "F10":121, "F11":122, "F12":123, "NUMLOCK":144, "SCROLLLOCK":145, "SEMICOLON":186, "EQUAL":187, "COMMA":188, "DASH":189, "PERIOD":190, "SLASH":191, "GRAVE":192, "OPENBRAKET":219, "BACKSLASH":220, "CLOSEBRAKET":221, "SINGLEQUOTE":222, "MMNEXT":176, "MMPREVIOUS":177, "MMSTOP":178, "MMPLAY":179, "MMREWIND":227, "MMFORWARD":228, "MYCOMPUTER":182, "MYCALCULATOR":183, "HELP":225, "Invalid!":0
}

you can use like

if(event.keyCode == Keys['RIGHT']) //go right
if(event.keyCode == Keys['LEFT']) //go left
if(event.keyCode == Keys['ENTER']) //do something
if(event.keyCode == Keys['ESC'] || event.keyCode == Keys['BACKSPACE']) //exit

You mentioned arrows and other keys, if you're using keys to bind something like a game, avoid using modifiers like CTRL ALT WINKEY ALTGR APPLICATION OPTION COMMAND they are a mess, there are so many inconsistencies, like Command key pretending to be Application key, the right alt as another control, etc, also some keyboards doesn't have a second alt, or ctrl. So its a hell of exceptions.