jQuery自定义动画animate函数的step属性

.animate是来实现自定义动画的,共有两种语法结构:

.animate( properties [, duration ] [, easing ] [, complete ] )
.animate( properties, options )

演示代码

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			li{
				width: 300px;height: 300px;
				background-color: red;
			}
		</style>
		<script src="https://cdn.bootcss.com/jquery/1.10.1/jquery.js"></script>
	</head>
	<body>
		<ul>
			<li></li>
		</ul>
		<script type="text/javascript">
			$( "li" ).animate({
			      opacity: .5,
			      height: "50%"
			    }, {
			      step: function( now, fx ) {
			        var data = fx.elem.id + " " + fx.prop + ": " + now;
			        $( "body" ).append( "<div>" + data + "</div>" );
			      }
			});
		</script>
	</body>
</html>

验证结果


opacity: 1
height: 4285.714285714285
opacity: 0.9681240017681993
height: 4015.6790435506023
opacity: 0.9451076018345824
height: 3820.6972555415337
opacity: 0.9267766952966369
height: 3665.408290155795
opacity: 0.915327966330913
height: 3568.4212004890196
opacity: 0.8905208444630326
height: 3358.2694395225476
opacity: 0.8721553103742388
height: 3202.6871293131935
opacity: 0.8510858988821862
height: 3024.199114816234
opacity: 0.8197477765098073
height: 2758.720449575939
opacity: 0.8006968238391281
height: 2597.3316648086134
opacity: 0.7774335777727613
height: 2400.258737417821
opacity: 0.7519634752221778
height: 2184.4905829535915
opacity: 0.7264729216703714
height: 1968.549179293289
opacity: 0.701227419495968
height: 1754.6837108729856
opacity: 0.6746155100138762
height: 1529.242820546122
opacity: 0.652518078052953
height: 1342.046004077159
opacity: 0.6312859025323514
height: 1162.1791457383483
opacity: 0.6078595373164339
height: 963.7243661235052
opacity: 0.5891360338165553
height: 805.10954361739
opacity: 0.5664193726410787
height: 612.6669710879951
opacity: 0.5524612469060775
height: 494.4217059329126
opacity: 0.5389180186244962
height: 379.69121491894657
opacity: 0.5263638400404937
height: 273.3393877716112
opacity: 0.5154521660193789
height: 180.90192070702506
opacity: 0.5078542097178422
height: 116.53637660972072
opacity: 0.5027783753138739
height: 73.53680801610335
opacity: 0.5002775312595076
height: 52.35108624125678
opacity: 0.5
height: 50