javascript 小型动画组件与实现代码

做一个普通的动画效果,js是怎么完成的呢.看一下例子

复制代码 代码如下:

setInterval(function(){
element.style.left =parseFloat(element.style.left) +(n) +'px';
},10);

<p id="test2" style="border:0px solid #00ff00;position:absolute;left:0px;top:400px;background:#0f0">test</p>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]

用window.setInterval 动画函数 ,每隔10毫秒 都会去执行一次动画 ;
和 set配套的是 clearInterval 函数，用来结束动画。
每隔setInterval 都会返回一个类似于线程id的值 ;
var interval =setInterval(function(){
element.style.left =parseFloat(element.style.left) +(n) +'px';
},10);
用 clearInterval (interval) 既可结束动画播放.
interval = setInterval(function(){
if(parseFloat(element.style.left)>500) clearInterval(interval)
element.style.left =parseFloat(element.style.left) +2 +'px';
},10);
超过500px的时候，动画就会停止， element将不在移动。

<p id="test2" style="border:0px solid #00ff00;position:absolute;left:0px;top:400px;background:#0f0">test</p>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]

但是上面的动画是比较生硬的，然后我们有另外一种时间线动画。
看例子:
var element = document.getElementById('test1');
var start = +new Date,dur=1000,finish = start+dur;
interval = setInterval(function(){
var time = +new Date,
pos = time > finish ? 1 : (time-start)/dur;
element.style.left = (100*pos)+"px";
if(time>finish) {
clearInterval(interval);
}
},10);
start 为目标动画的开始时间 ( +new Date 其实就是 new Date().getTime() )
dur 为 动画执行一共所需要的时间
finish 是目标动画结束的时间
pos = time > finish ? 1 : (time-start)/dur; //可以把pos 想象成频率 ，一个时间比
(100*pos) ，100代表距离,，如果距离为500px 就设置为 500*pos;
time>finish : 如果超过时间，就停止动画!

<p id="test2" style="border:0px solid #00ff00;position:absolute;left:0px;top:400px;background:#0f0">test</p>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]

很好，到这里我们已经知道一个简单动画效果是怎么样写的了.
再来看一个小型的完整的动画组件是如何写的 :

复制代码 代码如下:

(function($,name){
var parseEl = document.createElement('div')
,
props = ('backgroundColor borderBottomColor borderBottomWidth borderLeftColor borderLeftWidth '+
'borderRightColor borderRightWidth borderSpacing borderTopColor borderTopWidth bottom color fontSize '+
'fontWeight height left letterSpacing lineHeight marginBottom marginLeft marginRight marginTop maxHeight '+
'maxWidth minHeight minWidth opacity outlineColor outlineOffset outlineWidth paddingBottom paddingLeft '+
'paddingRight paddingTop right textIndent top width wordSpacing zIndex').split(' ')
,
normalize =function (style){
var css,
rules = {},
i = props.length,
v;
parseEl.innerHTML = '

';
css = parseEl.childNodes[0].style;
while(i--) if(v = css[props[i]]) rules[props[i]] = parse(v);
return rules;
},
color = function(source,target,pos){
var i = 2, j, c, tmp, v = [], r = [];
while(j=3,c=arguments[i-1],i--)
if(s(c,0)=='r') { c = c.match(/\d+/g); while(j--) v.push(~~c[j]); } else {
if(c.length==4) c='#'+s(c,1)+s(c,1)+s(c,2)+s(c,2)+s(c,3)+s(c,3);
while(j--) v.push(parseInt(s(c,1+j*2,2), 16)); }
while(j--) { tmp = ~~(v[j+3]+(v[j]-v[j+3])*pos); r.push(tmp255?255:tmp); }
return 'rgb('+r.join(',')+')';
},
parse = function(prop){
var p = parseFloat(prop), q = prop.replace(/^[\-\d\.]+/,'');
return isNaN(p) ? { v: q, f: color, u: ''} : { v: p, f: interpolate, u: q };
},
s = function(str, p, c){
return str.substr(p,c||1);//color 用
},
interpolate =function(source,target,pos){
return (source+(target-source)*pos).toFixed(3);
},
flower = function(el, style,opts,after){
var el = document.getElementById(el), //通过id获取元素对象
opts = opts || {},
target = normalize(style),
comp = el.currentStyle ? el.currentStyle : getComputedStyle(el, null), //ie和w3c兼容，获取样式
prop,
current = {},
start = +new Date, //开始时间
dur = opts.duration||200, //执行事件，默认为200
finish = start+dur, //结束时间
interval,
easing = opts.easing || function(pos){ return (-Math.cos(pos*Math.PI)/2) + 0.5; };
for(prop in target) current[prop] = parse(comp[prop]);
interval = setInterval(function(){
var time = +new Date,
pos = time>finish ? 1 : (time-start)/dur;
for(prop in target){
el.style[prop] = target[prop].f(current[prop].v,target[prop].v,easing(pos)) + target[prop].u;
}
if(time>finish) {
clearInterval(interval); opts.after && opts.after(); after && setTimeout(after,1);
}
},10);
};
$[name] = flower;
})(window,"flower");

复制代码 代码如下:

var parse = function(prop){
var p = parseFloat(prop), q = prop.replace(/^[\-\d\.]+/,'');
return isNaN(p) ? { v: q, f: color, u: ''} : { v: p, f: interpolate, u: q };
}
var p = parseFloat(prop) 意思是 : 500px => 500;
q = prop.replace(/^[\-\d\.]+/,''); 500px => px;
return isNaN(p) ? { v: q, f: color, u: ''} : { v: p, f: interpolate, u: q }; 意思是 如果取的是颜色值(因为带有#号)，返回{ v: q, f: color, u: ''} u 代表代为,f是一个color函数(后面会讲到);
var s = function(str, p, c){ return str.substr(p,c||1); }

s 函数是用来截取字符串，并将最后结果返回
color 函数 将颜色值，最后统一返回 "rgb(x,x,x)" 的形式
normalize 函数 返回一个json对象,对象里包含了该元素要执行的css属性名和值
while(i--) if(v = css[props[i]]) rules[props[i]] = parse(v);
把一行代码拆开，看看到底如何作用
while(i--){
//这里用了一个 =号， 先进行赋值运算，如果不存在之 if将不通过， 一举两得 : )
if(v = css[props[i]]){
rules[props[i]] = parse(v); //赋给新的对象,
}
}
interpolate函数中 return (source+(target-source)*pos).toFixed(3);
toFixed 是为了解决小数问题，如 0.000000001; 会变成 1e-9; 不是我们想要的结果，通过toFixed 可以解决， toFixed (n)， 其中n代表保留小数点后几位
el.currentStyle ? el.currentStyle : getComputedStyle(el, null);
这个其实兼容多浏览器,获取元素的一句代码 具体参考 : JS 获取最终样式 【getStyle】
flower的 4个参数 el 目标对象,style 是最终样式,opts,是参数选项包括 (dur时间,easing缓懂函数,after结束后运行的callbak) ,第4个after是最后执行的callbak;
opts.easing 可以利用各种缓动算法，来改变元素的运动状态;
如

复制代码 代码如下:

function bounce(pos) {
if (pos return (7.5625*pos*pos);
} else if (pos return (7.5625*(pos-=(1.5/2.75))*pos + .75);
} else if (pos return (7.5625*(pos-=(2.25/2.75))*pos + .9375);
} else {
return (7.5625*(pos-=(2.625/2.75))*pos + .984375);
}
}
(function($,name){
window.flower = flower;
})(window,'flower');

这样其实就是让内部函数自由，并且只通过这个调用去暴露一个接口。不然外面的函数，访问不到匿名函授中的flower;
看一下调用的例子 : )

复制代码 代码如下:

test

test

<script> <BR>(function($,name){ <BR>var parseEl = document.createElement('div') <BR>, <BR>props = ('backgroundColor borderBottomColor borderBottomWidth borderLeftColor borderLeftWidth '+ <BR>'borderRightColor borderRightWidth borderSpacing borderTopColor borderTopWidth bottom color fontSize '+ <BR>'fontWeight height left letterSpacing lineHeight marginBottom marginLeft marginRight marginTop maxHeight '+ <BR>'maxWidth minHeight minWidth opacity outlineColor outlineOffset outlineWidth paddingBottom paddingLeft '+ <BR>'paddingRight paddingTop right textIndent top width wordSpacing zIndex').split(' ') <BR>, <BR>normalize =function (style){ <BR>var css, <BR>rules = {}, <BR>i = props.length, <BR>v; <BR>parseEl.innerHTML = '<div style="'+style+'">'; <BR>css = parseEl.childNodes[0].style; <BR>while(i--) if(v = css[props[i]]) rules[props[i]] = parse(v); <BR>return rules; <BR>}, <BR>color = function(source,target,pos){ <BR>var i = 2, j, c, tmp, v = [], r = []; <BR>while(j=3,c=arguments[i-1],i--) <BR>if(s(c,0)=='r') { c = c.match(/\d+/g); while(j--) v.push(~~c[j]); } else { <BR>if(c.length==4) c='#'+s(c,1)+s(c,1)+s(c,2)+s(c,2)+s(c,3)+s(c,3); <BR>while(j--) v.push(parseInt(s(c,1+j*2,2), 16)); } <BR>while(j--) { tmp = ~~(v[j+3]+(v[j]-v[j+3])*pos); r.push(tmp<0?0:tmp>255?255:tmp); } <BR>return 'rgb('+r.join(',')+')'; <BR>}, <BR>parse = function(prop){ <BR>var p = parseFloat(prop), q = prop.replace(/^[\-\d\.]+/,''); <BR>return isNaN(p) ? { v: q, f: color, u: ''} : { v: p, f: interpolate, u: q }; <BR>}, <BR>s = function(str, p, c){ <BR>return str.substr(p,c||1); <BR>}, <BR>interpolate =function(source,target,pos){ <BR>return (source+(target-source)*pos).toFixed(3); <BR>}, <BR>flower = function(el, style,opts,after){ <BR>var el = document.getElementById(el), <BR>opts = opts || {}, <BR>target = normalize(style), <BR>comp = el.currentStyle ? el.currentStyle : getComputedStyle(el, null), <BR>prop, <BR>current = {}, <BR>start = +new Date, <BR>dur = opts.duration||200, <BR>finish = start+dur, <BR>interval, <BR>easing = opts.easing || function(pos){ return (-Math.cos(pos*Math.PI)/2) + 0.5; }; <BR>for(prop in target) current[prop] = parse(comp[prop]); <BR>interval = setInterval(function(){ <BR>var time = +new Date, <BR>pos = time>finish ? 1 : (time-start)/dur; <BR>for(prop in target){ <BR>el.style[prop] = target[prop].f(current[prop].v,target[prop].v,easing(pos)) + target[prop].u; <BR>} <BR>if(time>finish) { <BR>clearInterval(interval); opts.after && opts.after(); after && setTimeout(after,1); <BR>} <BR>},10); <BR>}; <BR>$[name] = flower; <BR>})(window,"flower"); <BR>(function(){ <BR>var bounce = function(pos) { <BR>if (pos < (1/2.75)) { <BR>return (7.5625*pos*pos); <BR>} else if (pos < (2/2.75)) { <BR>return (7.5625*(pos-=(1.5/2.75))*pos + .75); <BR>} else if (pos < (2.5/2.75)) { <BR>return (7.5625*(pos-=(2.25/2.75))*pos + .9375); <BR>} else { <BR>return (7.5625*(pos-=(2.625/2.75))*pos + .984375); <BR>} <BR>} <BR>flower('test2', 'left:300px;padding:10px;border:50px solid #ff0000', { <BR>duration: 1500, <BR>after: function(){ <BR>flower('test1', 'background:#0f0;left:100px;padding-bottom:100px;opacity:1', { <BR>duration: 1234, easing: bounce <BR>}); <BR>} <BR>}); <BR>})(); <BR></script>

参考 : http://scripty2.com/doc/scripty2%20fx/s2/fx/transitions.html