Вот что я использую в своих проектах (всего 753 байта):
(function($)
{
// check for native placeholder support. Borrowed from Modernizr.
var placeholderSupport = !!( 'placeholder' in document.createElement('input') );
$.fn.placeholder = function(text)
{
// if placeholder is supported natively, exit
if (placeholderSupport) return this;
// else:
return this.each(function()
{
var $this = $(this);
text = text || $this.attr('placeholder');
// if it's not a input element, exit
if ( this.tagName !== "INPUT" )
{
$.error('jquery.placeholder only works on "input" elements. Does not support "' + this.tagName.toLowerCase() + '" elements.');
return;
}
// If placeholder has already been applied, exit
if ( $this.data('jquery-placeholder') ) return;
// If not, let's mark it now as having placeholder applied
$this.data('jquery-placeholder', true);
// if its value is empty, let's add the placeholder text
if ( $this.val() === '' )
{
$this.val( text ).addClass('placeholder');
}
// Now, let's setup the focus & blur events, to add and remove the text & the class, respectively.
$this.focus(function()
{
var $this = $(this);
if ( $this.val() === text && $this.hasClass('placeholder') )
{
$this.val('').removeClass('placeholder');
}
})
.blur(function()
{
var $this = $(this);
if ( $this.val() === '')
{
$this.val( text ).addClass('placeholder');
}
});
});
};
// Now, before we leave, let's just make sure that these placeholder values never get submitted
placeholderSupport || $(document).delegate('form', 'submit', function()
{
$(this)
.find('.placeholder')
.val('').removeClass('placeholder');
});
})(jQuery);
Вот сокращенная версия:
(function(b){var d=!!("placeholder"in document.createElement("input"));b.fn.placeholder=function(c){return d?this:this.each(function(){var a=b(this);c=c||a.attr("placeholder");"INPUT"!==this.tagName?b.error('jquery.placeholder only works on "input" elements. Does not support "'+this.tagName.toLowerCase()+'" elements.'):a.data("jquery-placeholder")||(a.data("jquery-placeholder",!0),""===a.val()&&a.val(c).addClass("placeholder"),a.focus(function(){var a=b(this);a.val()===c&&a.hasClass("placeholder")&&a.val("").removeClass("placeholder")}).blur(function(){var a=b(this);""===a.val()&&a.val(c).addClass("placeholder")}))})};d||b(document).delegate("form","submit",function(){b(this).find(".placeholder").val("").removeClass("placeholder")})})(jQuery);
Затем, чтобы использовать его, просто запустите его на готовом документе:
$('input[placeholder]').placeholder();
Вот скрипка: http://jsfiddle.net/vNkPD