Disable Button during ajax request

jquery.disabled.js

$.fn.extend({

 // add disabled class to elements
    disable: function(state) {
        return this.each(function() {
            $(this).addClass('disabled');
        });
    },

    // remove class disabled to element
    enable: function(state) {
        return this.each(function() {
            $(this).removeClass('disabled');
        });
    }
}

jQuery( document ).ajaxSend(function(e) {
          jQuery('.btn').disable();
      });

jQuery( document ).ajaxStop(function() {
    if (jQuery.active == 0) {
        jQuery('.btn').enable();
    }
});