jQuery keyboard events - w3toppers.com

You can use the input event, which works in recent versions of all major browsers:

var input = document.getElementById("your_input_id");
input.oninput = function() {
    alert(input.value);
};

Unfortunately, it doesn’t work in IE <= 8. However, in those browsers you can use the propertychange event on the value property instead:

input.onpropertychange = function() {
    if (window.event.propertyName == "value") {
        alert(input.value);
    }
};