Knockout + Bootstrap 3 - Buttons and the `enable` binding

knockout-boostrap-enable-btn.js

/**
Enhanced `enable` binding that adds disabled attribute to .btn elements
to support Bootstrap styling.

NOTE: This also effects the `disable` binding handler, since it simply
      inverts the `enable` bindings logic internally.

@static
@class Enable
@namespace Base.BindingHandlers
**/
var oldEnable = ko.bindingHandlers.enable,
      rIsBtn = /\bbtn\b/;

ko.bindingHandlers.enable = {
    update: function (element, valueAccessor) {
        var result = oldEnable.update.apply(this, arguments),
            enabled = ko.unwrap(valueAccessor());

        // Toggle `disabled` class on all `btn` elements
        if(rIsBtn.test(element.className)) {
            if(enabled) {
                element.className.replace(/\bdisabled\b/gi, '');
            }
            else {
                element.className += ' disabled';
            }
        }

        return result;
    }
};