随窗体滑动的小插件sticky源码_javascript技巧

$.fn.stickyfloat = function(options, lockBottom) {
var $obj = this;
var parentPaddingTop = parseInt($obj.parent().css('padding-top'));
var startOffset = $obj.parent().offset().top;
var opts = $.extend({ startOffset: startOffset, offsetY: parentPaddingTop, duration: 200, lockBottom:true }, options);

$obj.css({ position: 'absolute' });

if(opts.lockBottom){
var bottomPos = $obj.parent().height() - $obj.height() + parentPaddingTop;
if( bottomPos < 0 )
bottomPos = 0;
}

$(window).scroll(function () {
$obj.stop();

var pastStartOffset = $(document).scrollTop() > opts.startOffset;
var objFartherThanTopPos = $obj.offset().top > startOffset;
var objBiggerThanWindow = $obj.outerHeight() < $(window).height();

if( (pastStartOffset || objFartherThanTopPos) && objBiggerThanWindow ){
var newpos = ($(document).scrollTop() -startOffset + opts.offsetY );
if ( newpos > bottomPos )
newpos = bottomPos;
if ( $(document).scrollTop() < opts.startOffset )
newpos = parentPaddingTop;

$obj.animate({ top: newpos }, opts.duration );
}
});
};

$('#menu15').stickyfloat({ duration: 500 });
$('#menu14').stickyfloat({ duration: 500 });
$('#menu13').stickyfloat({ duration: 500 });
$('#menu12').stickyfloat({ duration: 500 });