How to allow numbers, backspace, delete, left and right arrow keys in the html text?

Question

I am using following javascript code which I think should only allow numbers, backspace, delet, left arrow and right arrow keys in textbox, but it is also allowing alphabets. I

Answer 1

const validateQty = (event) => {
    var key = window.event ? event.keyCode : event.which;
    console.log(event);
    if (event.keyCode === 8 || event.keyCode === 46
        || event.keyCode === 37 || event.keyCode === 39) {
        return true;
    } else if (key < 48 || key > 57) {
        return false;
    } else { return true; }
};