javascript limit text input characters

Question

I am wanting to restrict the input characters for a text box to [a-z0-9_-]. However whenever if do this buttons like backspace and the arrow keys don\'t work. I have found s

Answer 1

Yes you can limit the input of characters. For example create a function that checks what is going on, return true if everything is OK and false if not:

// return true for 1234567890A-Za-z - _
function InputCheck(e) {
    if ((e.shiftKey && e.keyCode == 45) || e.which != 8 && e.which != 0 && (e.which < 48 || e.which > 57)) {
        if (e.which == 45 || e.which == 95 || (e.which >= 65 && e.which <= 90) || (e.which >= 97 && e.which <= 122))
            return true;
        return false;
    }
    return true;
}

once you have the function, hook it into you input (this is with jQuery):

$('#InputID').keypress(InputCheck);

You can make as complicated a check as you want, for example this will allow for USD money values:

function InputCheck(e) {
    if ((e.shiftKey && e.keyCode == 45) || e.which != 8 && e.which != 0 && (e.which < 48 || e.which > 57) && e.which != 46 && e.which != 36) {
        return false;
    }
    // . = 46
    // $ = 36
    var text = $(this).val();

    // Dollar sign first char only
    if (e.which == 36 && text.length != 0) {
        return false;
    }

    // Only one decimal point
    if (e.which == 46 && text.indexOf('.') != -1) {
        return false;
    }

    // Only 2 numbers after decimal
    if (text.indexOf('.') != -1 && (text.length - text.indexOf('.')) > 2) {
        return false;
    }

    return true;
}