How to prevent invalid characters from being typed into input fields

Question

Onkeydown, I run the following JavaScript:

function ThisOnKeyDown(el) {
   if (el.title == \'textonly\') {
       !(/^[A-Za-zÑñ-\\s]*$/i).test(e         


        

Answer 1

To prevent it from being set in the first place, you can return false on the keydown event handler, thus preventing the event from propagating any further.

I wrote the example below using jQuery, but you can use the same function when binding traditionally.

Though it's important to validate on the server-side as well, client-side validation is important for the sake of user friendliness.

$("input.number-only").bind({
    keydown: function(e) {
        if (e.shiftKey === true ) {
            if (e.which == 9) {
                return true;
            }
            return false;
        }
        if (e.which > 57) {
            return false;
        }
        if (e.which==32) {
            return false;
        }
        return true;
    }
});