Disable zero as first letter in <input>

Question

Below code disables 0 as the first character in #foo.
However, you can bypass this by typing 123, then drag to select 123

Answer 1

If you want to catch the changes to the input's value (including the changes made by dragging part of the text for example), you can watch the input event.

$('input#foo').on("input", function(){
  alert($(this).val());
});