Q:

jQuery live check input changes

I am stuck with a new code, and I seek a smart one-way efficient solution. 
I want to accomplish something similar to Twitter, Let's say we have two
inputs of type=Text, and once one changes we either removeAttr("disabled", "disables"); or attr("disabled", "disabled"), I know this is easy to accomplish when checking one field, but lets say I changed on Field, and next I change the other field, and all of the sudden I decide to change one of them back, or vice versa or both back to previous values, so that the submit button changes between disabled/enabled. 
Here's my jsfiddle: http://jsfiddle.net/Xu9XH/
<input type="text" value="Carl" name="first_name" maxlength="15" id="firstname" />
<input type="text" value="Johnson" name="last_name" maxlength="15" id="lastname" />
<br /><br />
<button id="senddata" disabled="" type="submit">Submit</button>

A:

var inputs = $('input[type="text"]'),
    button = $('#senddata');

inputs.each(function() {
    $(this).data('val', this.value);
}).on('keyup', function() {
    var state = true;
    inputs.each(function(i,el) {
        if ( $(el).val() != $(el).data('val')) state = false;
    });
    button.prop('disabled', state);
});

FIDDLE

