每日一库：Émile.js

Émile.js是一个小型的动画库，只有短短几十行代码，但是做简单的动画足够应付了。 如果有时你不想引入巨大的基础库，想试试‘小米加步枪’的作业方式，可以参考下。 这样的动画库，现在看起来可能有点简陋了，但是还是可以学到一些基本原理。以下是源码分析和一些例子： 

emile.js 例子

①改变颜色

 

emile($('example_1'), 'background-color: rgb(0, 0, 0)', {duration: 500});

Run | Reset

②直线运动

 

emile($('example_2'), 'margin-left: 200px', {duration: 500});

Run | Reset

③定制运动算法

 

function bounce(pos) {
  if (pos < (1 / 2.75)) {
    return (7.5625 * pos * pos);
  } else if (pos < (2 / 2.75)) {
    return (7.5625 * (pos -= (1.5 / 2.75)) * pos + .75);
  } else if (pos < (2.5 / 2.75)) {
    return (7.5625 * (pos -= (2.25 / 2.75)) * pos + .9375);
  } else {
    return (7.5625 * (pos -= (2.625 / 2.75)) * pos + .984375);
  }
}
emile($('example_3'), 'margin-left: 200px', {duration: 1500, easing: bounce});

Run | Reset

④同时改变颜色和直线运动

 

emile($('example_4'), 'margin-left: 200px; background-color: #000', {duration: 1500, easing: bounce});

Run | Reset

⑤回调函数

 

emile($('example_5'), 'margin-left: 200px; background-color: #000', {
  duration: 1500,
  easing: bounce,
  after: function() { emile($('example_5'), 'margin-left: 0; opacity: 0.0', {duration: 1500}); }});
    

Run | Reset

(function(emile, container){
  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(' ');

  function interpolate(source,target,pos){ return (source+(target-source)*pos).toFixed(3); } // interpolate 插入，插（话）

  function s(str, p, c){ return str.substr(p,c||1); }
  function color(source,target,pos){ //如果是颜色，调用此函数；其余的调用interpolate
    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(tmp<0?0:tmp>255?255:tmp); }
    return 'rgb('+r.join(',')+')';
  }
  
  function parse(prop){ //对值进行处理
    var p = parseFloat(prop), q = prop.replace(/^[\-\d\.]+/,'');
    return isNaN(p) ? { v: q, f: color, u: ''} : { v: p, f: interpolate, u: q }; //v值 f运动函数 q单位
  }
  
  function normalize(style){
    var css, rules = {}, i = props.length, v;
    parseEl.innerHTML = '<div style="'+style+'"></div>';
    css = parseEl.childNodes[0].style;
    
    while(i--) if(v = css[props[i]]) rules[props[i]] = parse(v);
    
    return rules;
  }  
  
  container[emile] = function(el, style, opts, after){
    el = typeof el == 'string' ? document.getElementById(el) : el; //运动元素
    opts = opts || {}; //参数项
    var target = normalize(style), //正常化样式
      comp = el.currentStyle ? el.currentStyle : getComputedStyle(el, null),
      prop, 
      current = {},
      start = +new Date,
      dur = opts.duration||200,  //运动持续时间
      finish = start+dur,  //结束时间
      interval,
      easing = opts.easing || function(pos){ return (-Math.cos(pos*Math.PI)/2) + 0.5; }; //运动算法

    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) { //运动结束，调用回调函数
        clearInterval(interval); 
        opts.after && opts.after();  //回调有2种形式，一种可以放入opts，一种可以作为第四个参数
        after && setTimeout(after,1);
      }
    },10);
  }
})('emile', this);

//测试用
function $(element) { return document.getElementById(element); }
function bounce(pos) {
  if (pos < (1 / 2.75)) {
    return (7.5625 * pos * pos);
  } else if (pos < (2 / 2.75)) {
    return (7.5625 * (pos -= (1.5 / 2.75)) * pos + .75);
  } else if (pos < (2.5 / 2.75)) {
    return (7.5625 * (pos -= (2.25 / 2.75)) * pos + .9375);
  } else {
    return (7.5625 * (pos -= (2.625 / 2.75)) * pos + .984375);
  }
}