Text field placeholders with jQuery.

placeholder.js

/* Text field placeholders
 * 
 * Dave Gurnell, http://www.untyped.com
 *
 * Example usage: $("#my-date-field").placeholder("yyyy-mm-dd");
 */
(function ($) {
        
        // -> Boolean
        $.fn.hasPlaceholder = function () {
                return $(this).data("placeholder") === true;
        };
        
        // String [String] -> jQuery
        $.fn.placeholder = function (text, cssClass) {
                return $(this).each(function () {
                        
                        if(!text) {
                                throw "No text specified for placeholder.";
                        }
                        
                        cssClass = cssClass || "placeholder";
                
                        var $this = $(this);

                        function onFocus () {
                                if($this.hasPlaceholder()) {
                                        $this.val("").removeClass(cssClass).removeData("placeholder");
                                }
                        }
                
                        function onBlur () {
                                if($this.val() == "") {
                                        $this.val(text).addClass(cssClass).data("placeholder", true);
                                }
                        }               
                
                        $this.focus(onFocus).blur(onBlur);
                
                        onBlur();
                });
        };
        
})(jQuery);