javascript (jquery) numeric input: keyCode for 

问题:

I need to set up an <input type="text" /> so that it will accept only numeric chars, backspace, delete, enter, tabs and arrows.

There's a lot of exemple around there, i started with something similar to this:

function isNumericKeyCode (keyCode){
    return ( (keyCode >= 48 && keyCode <= 57) //standard keyboard
           ||(keyCode >= 96 && keyCode <= 105)) //Numpad
}

$('#myTextBox').keydown(function(e){
         var handled = true;
         var keyCode = e.keyCode;
         switch(keyCode){
            //Enter and arrows
            case 13:
            case 37:
            case 38:
            case 39:
            case 40:
               doSomethingSpecialsWithThesesKeys();
               break;
            default:
               handled = false;
               break;
         }

         if (  !handled
            && keyCode !== 8 //backspace
            && keyCode !== 9 //tab
            && keyCode !== 46 //del
            && !isNumericKeyCode(keyCode)){

            handled = true;
         }

         return handled;
});

All that worked perfectly until I hit the "#" key. In my french canadian keyboard, the "#" has his own key (no shift implied) that returns keyCode 51, the same as the number "3".

I think that in US keyboard, the "#" is obtained by pressing shift+3, that may be why they have the same keycode.

Now I realize that I have to handle the shift and alt keys too, but that's another story.

It works differently with the jquery keypress event, which offer the charCode property, but I did not used it at first because of what the documentation says :

as the keypress event isn't covered by any official specification, the actual behavior encountered when using it may differ across browsers, browser versions, and platforms.

Also, I would need a workaround in that case to handle tabs, arrows and other special keys since they don't provide a charCode.

So the question is : is there a way to allow only some specifics chars using the keydown event? And that, in a way that will work independently of the keyboard layout?

As a side quest : Which browsers may be problematics with the keypress event? I mean, currently I don't really care if my website does not support IE6. I am targetting recent browsers.

Edit

---

As someone pointed out in the comments, this method does not allow user to "ctrl+v" a number in the input. In my particular case this is really not a requirement to be able to paste a number. But this popped something in my head, the user still can right-clic > copy some text in the input, and in that case that could be anything. The more I think of it, the more it seems to me that I will need the keydown event to handle tabs and arrows, and another event to handle the input itself.

Edit2

---

A lot of beautiful answers here, but the award goes to mrtsherman for the use of input and propertychange events. I will use a combination of this answer for the numeric validation, plus the keyCode event as before for the special use of arrows, tabs and enter keys.

回答1:

How about something like this. This should cover cut/paste and also rmb content. We monitor the textbox for any change in content. Then we use a regex to filter out characters based on a whitelist. This won't handle non-character key, but I think that is okay.

The \d flag says that only digits should be accepted.

http://jsfiddle.net/UXeva/1

$('#myTextBox').bind('input propertychange', function() {
    var text = $(this).val();
    if (isNaN(text)) {
       $(this).val(text.replace(/[^\d]/gi, ''));
    }
});

We bind to two events here. input for FireFox and propertychange for other browsers.

回答2:

If older browsers are'nt an issue, the number input type should cover this.

<input type="number" />

If not you could use the isNaN javascript function

$("#number1").on('keyup', function() {
    var myval = $(this).val();
    if (isNaN(myval)) {
        alert('numbers only!');
    }
});

Personally I would do some regex filtering with a check to see if the value has changed, that will allow any character that does not change the value, like tabs, enter and arrows. With a regex you could also add or remove any character, or you could use \d for digits only or as below, [0-9]. Up to you really what your exact needs are?

var P;
$("#number2").on('keyup', function() {
    var V = $(this).val();
    if (V != P) {
        $(this).val(V.replace(/[^0-9]/g,''));
    }
    P=V;
});

They could also be combined to something like this:

$("#number3").on('keyup', function() {
    var V = $(this).val();
    if (isNaN(V)) {
        $(this).val(V.replace(/[^0-9]/g,''));
    }
});

Here's a FIDDLE to test them out!

回答3:

Why not do something like this? It uses a combination of the keyup() event and isNaN(). It'll work whether the user types with the keyboard or pastes a number.

The way it works is, as soon as the text changes, it will check if the value is a number. If not, it will trim the input until it is a number. So, if you enter 25s or 25ss, you will be left with 25.

This will work with ctrl+v paste as well. It won't work with right-click paste and for that reason, I have disabled right-clicking only on the textbox.

Live Demo

The Jquery

$(document).ready(function(){
    $('#number').keyup(function(){    
        var input = this.value;
        while (isNaN(input))
        {
            input = input.substring(0,input.length-1);
            $('#number').val(input);             
        }
    });
    $('#number').bind("contextmenu",function(e){
        return false;
    });
});

回答4:

jQuery also provides a shiftkey boolean on the event object:

$('#myTextBox').keydown(function(e){
  if(e.keyCode === 51 && !e.shiftKey){
     // '3' key pressed while shift was **not** held down (not '#')
  }
});

EDIT I reread your question and changed the code above for !shiftkey