Jquery Keydown and Characters

Question

I need to catch some characters from keyboard and I have to use jquery keydown(not keypress).

I know some of you will recommend to use keypress but I have to use keydown and I only need 3 characters to catch with keydown function.(chars: A,F,X)

Here is my code.

$("#keypage").keydown(function(e){
  var keycode = e.keyCode;
  if( keycode === 65 || keycode === 70 || keycode === 88) {
    var char = String.fromCharCode(keycode);
  }

  // do something with char
});

Is there a problem with that approach?

EDIT: I asked this question because I want to know that if keydown has a problem for chars with this approach.

It's a dummy name.You can think keypage as an input or something like that. — javauser35, Aug 31 '17 at 12:57
People usually recommend to use keypress for chars.But I need to use keydown.I ask this question because I want to know that if keydown has a problem for chars with this approach. — javauser35, Aug 31 '17 at 13:00
make sure to do `e.preventDefault()` if you dont want the charcter to be inserted in the input field — Joel Harkes, Aug 31 '17 at 13:01
Deleted my answer by reading above comment , As you were asking whether we should use kepdown or not. — amit wadhwani, Aug 31 '17 at 13:14
Please check this link, then you will understand the main differences between key press and key down. https://stackoverflow.com/questions/1367700/whats-the-difference-between-keydown-and-keypress-in-net — Libin C Jacob, Aug 31 '17 at 13:18
"*Is there a problem with that approach?*" - does it work? Also when holding down a key? Do you care if it's "a" or "A" ? — freedomn-m, Aug 31 '17 at 13:19
Note that the link from @LibinCJacob is for .net - js is *slightly* different (you only get one keydown/keyup but many keypress when holding down a key). — freedomn-m, Aug 31 '17 at 13:20

Ghulam Mohayudin · Answer 1 · 2017-08-31T13:35:29.913

If you just wanted to check only the mentioned Characters then it is fine to use keydown

The keypress events are generally the easiest to work with. They are likely to cause substantially fewer problems with non-US keyboard layouts and it's not too hard to identify which key was pressed. You can get the character typed by doing:

if (event.which == null)
  char= String.fromCharCode(event.keyCode);    // old IE   
else if (event.which != 0 && event.charCode != 0)
  char= String.fromCharCode(event.which);     // All others   
else
  // special key

What to do with keypress events on special keys is a problem. I recommend pretending they never happened. If you really want to process special key events, you should probably be working with keydown and keyup instead. For keydown and keyup events, you can identify most common keys (letters, numbers, and a few others) by just looking at the event.keyCode and more or less pretending that it is an ASCII code. However, it isn't really, and the many Javascript manuals that say it can be converted to a character by doing String.fromCharCode(event.keyCode) are wrong. On keydown and keyup events, the keycodes are not character codes, and this conversion will give wild results for many keys. There is no general portable way to convert keycodes to characters.

Because of bugs, many keys cannot be distinguished on keydown and keyup in Macintosh Gecko.

Now if you need to check complex key codes and their hashes then keypress is the best option. for more details you can read keydown, keypress and keyup events detail on this link

Jquery Keydown and Characters

1 Answers1