Makes sure that <input type="number"> only accepts numbers and not letters.

Numbers Only

// make sure that input type="number" only accepts numbers
$.fn.allowNumbersOnly = function() {
    $(this).keydown(function (event) {
        var num = event.keyCode;
        if ((num > 95 && num < 106) || (num > 36 && num < 41) || num == 9) {
            return;
        }
        if (event.shiftKey || event.ctrlKey || event.altKey) {
            event.preventDefault();
        } else if (num != 8 && num != 46 && num != 109 && num != 110 && num != 188 && num != 189 && num != 190) {
            // 8 backspace, 46 delete, 109 subtract, 110 decimal, 188 comma, 189 dash, 190 period
            // reference: http://www.cambiaresearch.com/articles/15/javascript-char-codes-key-codes
            if (isNaN(parseInt(String.fromCharCode(event.which)))) {
                event.preventDefault();
            }
        }
    });
}