jquery keyup function check if number

I decided to use the answer provided by @Rahul Yadav, but it is erroneous since it doesn't consider num pad keys, which have different codes.

Here, you can see a excerpt of the code table:

Here the function I implemented:

function isNumberKey(e) {
    var result = false; 
    try {
        var charCode = (e.which) ? e.which : e.keyCode;
        if ((charCode >= 48 && charCode <= 57) || (charCode >= 96 && charCode <= 105)) {
            result = true;
        }
    }
    catch(err) {
        //console.log(err);
    }
    return result;
}

Try binding to the keypress event instead of keyup. It gets fired repeatedly when a key is held down. When the key pressed is not a number you can call preventDefault() which will keep the key from being placed in the input tag.

   $('#p_first').keypress(function(event){

       if(event.which != 8 && isNaN(String.fromCharCode(event.which))){
           event.preventDefault(); //stop character from entering input
       }

   });

Working Example: http://jsfiddle.net/rTWrb/2/