Prevent backspace navigation to previous page

HTML

<h4>read-write</h4>
<input type='text' value='try to erase' />
<h4>readonly</h4>
<input type='text' readonly='readonly' value='try to erase' />

JavaScript

$(document).on("keydown", function (e) {
debugger;
    if (e.which === 8) {
        e.preventDefault();
    }
});