原生js 动画效果的实现
昨天写《锋利的JQ》里的动画案例卡住了,切换都成功了,但没有动画效果,按自己
以前学的动画知识,在那里连接不上。不得已继续搜寻资料学习动画。
看了一个“CJ”的javascript视频教程,觉得里面讲的动画挺不错的。有必要记录下。
首先,我们知道,最常见的动画莫过于移动,一般都是通过修改
node.style['left' | 'top']这样实现。那么,我们可以构建这么一个小例子,如结构:
- <style type="text/css">
- #test{ width:100px; height:100px; background:red; position:absolute; left:100px; top:200px;}
- </style>
- </head>
- <body>
- <div id="test">test</div>
- </body>
我们想让它从距左边100个px移动到200px,看JS代码:
- window.onload = function(){
- var test = document.getElementById("test");
- test.style.left = test.offsetLeft + 100 + "px"; //offsetLeft获取元素的实际坐标,test.style.left只获取嵌入在html里的样式,而且带单位,如"px"
- }
上面是动了,但是就像”瞬移“一样,直达目的地,这样不好,我们不止要让它动,还
要让它动得好看点。
我们知道setInterval可以让我们循环执行,那么,就有了下面代码:
- window.onload = function(){
- var test = document.getElementById("test");
- var interval = setInterval(function(){
- if(test.offsetLeft >= 200){
- clearInterval(interval); //当条件满足时,清除setInterval
- return;
- }
- test.style.left = test.offsetLeft + 1 + "px"; //每次递增1像素
- },50)
- }
这样,效果就慢慢的移像我们指定的位置了。
这里,通过运行代码后可以发现,这是慢慢移动了,但是匀速运动,看起来也不是
那么好看,我们需要让他在规定时间内,就移动到我们所在的位置。
为了实现要求,网上有这么一个算法库,就是实现动画的不同效果的,如下:
- var Tween = {
- Linear:function (start,alter,curTime,dur) {return start+curTime/dur*alter;},//最简单的线性变化,即匀速运动
- Quad:{//二次方缓动
- easeIn:function (start,alter,curTime,dur) {
- return start+Math.pow(curTime/dur,2)*alter;
- },
- easeOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur;
- return start-(Math.pow(progress,2)-2*progress)*alter;
- },
- easeInOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur*2;
- return (progress<1?Math.pow(progress,2):-((--progress)*(progress-2) - 1))*alter/2+start;
- }
- },
- Cubic:{//三次方缓动
- easeIn:function (start,alter,curTime,dur) {
- return start+Math.pow(curTime/dur,3)*alter;
- },
- easeOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur;
- return start-(Math.pow(progress,3)-Math.pow(progress,2)+1)*alter;
- },
- easeInOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur*2;
- return (progress<1?Math.pow(progress,3):((progress-=2)*Math.pow(progress,2) + 2))*alter/2+start;
- }
- },
- Quart:{//四次方缓动
- easeIn:function (start,alter,curTime,dur) {
- return start+Math.pow(curTime/dur,4)*alter;
- },
- easeOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur;
- return start-(Math.pow(progress,4)-Math.pow(progress,3)-1)*alter;
- },
- easeInOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur*2;
- return (progress<1?Math.pow(progress,4):-((progress-=2)*Math.pow(progress,3) - 2))*alter/2+start;
- }
- },
- Quint:{//五次方缓动
- easeIn:function (start,alter,curTime,dur) {
- return start+Math.pow(curTime/dur,5)*alter;
- },
- easeOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur;
- return start-(Math.pow(progress,5)-Math.pow(progress,4)+1)*alter;
- },
- easeInOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur*2;
- return (progress<1?Math.pow(progress,5):((progress-=2)*Math.pow(progress,4) +2))*alter/2+start;
- }
- },
- Sine :{//正弦曲线缓动
- easeIn:function (start,alter,curTime,dur) {
- return start-(Math.cos(curTime/dur*Math.PI/2)-1)*alter;
- },
- easeOut:function (start,alter,curTime,dur) {
- return start+Math.sin(curTime/dur*Math.PI/2)*alter;
- },
- easeInOut:function (start,alter,curTime,dur) {
- return start-(Math.cos(curTime/dur*Math.PI/2)-1)*alter/2;
- }
- },
- Expo: {//指数曲线缓动
- easeIn:function (start,alter,curTime,dur) {
- return curTime?(start+alter*Math.pow(2,10*(curTime/dur-1))):start;
- },
- easeOut:function (start,alter,curTime,dur) {
- return (curTime==dur)?(start+alter):(start-(Math.pow(2,-10*curTime/dur)+1)*alter);
- },
- easeInOut:function (start,alter,curTime,dur) {
- if (!curTime) {return start;}
- if (curTime==dur) {return start+alter;}
- var progress =curTime/dur*2;
- if (progress < 1) {
- return alter/2*Math.pow(2,10* (progress-1))+start;
- } else {
- return alter/2* (-Math.pow(2, -10*--progress) + 2) +start;
- }
- }
- },
- Circ :{//圆形曲线缓动
- easeIn:function (start,alter,curTime,dur) {
- return start-alter*Math.sqrt(-Math.pow(curTime/dur,2));
- },
- easeOut:function (start,alter,curTime,dur) {
- return start+alter*Math.sqrt(1-Math.pow(curTime/dur-1));
- },
- easeInOut:function (start,alter,curTime,dur) {
- var progress =curTime/dur*2;
- return
(progress<1?1-Math.sqrt(1-Math.pow(progress,2)):(Math.sqrt(1 -
Math.pow(progress-2,2)) + 1))*alter/2+start;
- }
- },
- Elastic: {//指数衰减的正弦曲线缓动
- easeIn:function (start,alter,curTime,dur,extent,cycle) {
- if (!curTime) {return start;}
- if ((curTime==dur)==1) {return start+alter;}
- if (!cycle) {cycle=dur*0.3;}
- var s;
- if (!extent || extent< Math.abs(alter)) {
- extent=alter;
- s = cycle/4;
- } else {s=cycle/(Math.PI*2)*Math.asin(alter/extent);}
- return start-extent*Math.pow(2,10*(curTime/dur-1)) * Math.sin((curTime-dur-s)*(2*Math.PI)/cycle);
- },
- easeOut:function (start,alter,curTime,dur,extent,cycle) {
- if (!curTime) {return start;}
- if (curTime==dur) {return start+alter;}
- if (!cycle) {cycle=dur*0.3;}
- var s;
- if (!extent || extent< Math.abs(alter)) {
- extent=alter;
- s =cycle/4;
- } else {s=cycle/(Math.PI*2)*Math.asin(alter/extent);}
- return start+alter+extent*Math.pow(2,-curTime/dur*10)*Math.sin((curTime-s)*(2*Math.PI)/cycle);
- },
- easeInOut:function (start,alter,curTime,dur,extent,cycle) {
- if (!curTime) {return start;}
- if (curTime==dur) {return start+alter;}
- if (!cycle) {cycle=dur*0.45;}
- var s;
- if (!extent || extent< Math.abs(alter)) {
- extent=alter;
- s =cycle/4;
- } else {s=cycle/(Math.PI*2)*Math.asin(alter/extent);}
- var progress = curTime/dur*2;
- if (progress<1) {
- return start-0.5*extent*Math.pow(2,10*(progress-=1))*Math.sin( (progress*dur-s)*(2*Math.PI)/cycle);
- } else {
- return start+alter+0.5*extent*Math.pow(2,-10*(progress-=1)) * Math.sin( (progress*dur-s)*(2*Math.PI)/cycle);
- }
- }
- },
- Back:{
- easeIn: function (start,alter,curTime,dur,s){
- if (typeof s == "undefined") {s = 1.70158;}
- return start+alter*(curTime/=dur)*curTime*((s+1)*curTime - s);
- },
- easeOut: function (start,alter,curTime,dur,s) {
- if (typeof s == "undefined") {s = 1.70158;}
- return start+alter*((curTime=curTime/dur-1)*curTime*((s+1)*curTime + s) + 1);
- },
- easeInOut: function (start,alter,curTime,dur,s){
- if (typeof s == "undefined") {s = 1.70158;}
- if ((curTime/=dur/2) < 1) {
- return start+alter/2*(Math.pow(curTime,2)*(((s*=(1.525))+1)*curTime- s));
- }
- return start+alter/2*((curTime-=2)*curTime*(((s*=(1.525))+1)*curTime+ s)+2);
- }
- },
- Bounce:{
- easeIn: function(start,alter,curTime,dur){
- return start+alter-Tween.Bounce.easeOut(0,alter,dur-curTime,dur);
- },
- easeOut: function(start,alter,curTime,dur){
- if ((curTime/=dur) < (1/2.75)) {
- return alter*(7.5625*Math.pow(curTime,2))+start;
- } else if (curTime < (2/2.75)) {
- return alter*(7.5625*(curTime-=(1.5/2.75))*curTime + .75)+start;
- } else if (curTime< (2.5/2.75)) {
- return alter*(7.5625*(curTime-=(2.25/2.75))*curTime + .9375)+start;
- } else {
- return alter*(7.5625*(curTime-=(2.625/2.75))*curTime + .984375)+start;
- }
- },
- easeInOut: function (start,alter,curTime,dur){
- if (curTime< dur/2) {
- return Tween.Bounce.easeIn(0,alter,curTime*2,dur) *0.5+start;
- } else {
- return Tween.Bounce.easeOut(0,alter,curTime*2-dur,dur) *0.5 + alter*0.5 +start;
- }
- }
- }
- };
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