I'm trying to disable the submit button until all inputs have some data. Right now the button is disabled, but it stays disabled after all inputs are filled in. What am I doing wrong? 

```
$(document).ready(function (){
    validate();
    $('input').on('keyup', validate);
});

function validate(){
    if ($('input').val().length > 0) {
        $("input[type=submit]").prop("disabled", false);
    } else {
        $("input[type=submit]").prop("disabled", true);
    }
} 

```