原生JS实现星级评分系统：从原理到完整代码

完整代码实现

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title></title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    #star{
      position: absolute;
      left: 0;
      right: 0;
      top: 30px;
      bottom: 0;
      margin: auto;
      width: 80%;
      font-size: 12px;
    }
    #star-div{
      margin:5px;
      font-size: 0;
    }
    #star-div a{
      display: inline-block;
      width: 21px;
      height: 21px;
      background: url(http://files.cnblogs.com/files/susufufu/star0.gif) no-repeat;

    }
    #star-div .on{
      background: url(http://files.cnblogs.com/files/susufufu/star1.gif) no-repeat;
    }
    #star-info{
      position: absolute;
      top: 55px;
      left: -30px;
      display: none;
      width: 155px;
      height: 50px;
      padding: 2px;
      line-height: 17px;
      border-radius: 8px;
      background-color: gold;
      z-index: 5;
    }
    #star-info:before{
      content: '';
      border-bottom: 10px solid gold;
      border-left: 10px solid rgba(0,0,0,0);
      border-right: 10px solid rgba(0,0,0,0);
      position: absolute;
      left: 35px;
      top: -10px;
    }
    #star-span{line-height: 14px}
    #star-info strong,#star-span strong{
      color: red;
    }
  </style>
  <script>
    window.onload = function(){
      var sufuStar = function (){
        //工具函数
        function gbyId(id){return document.getElementById(id);}

        function addEvent(elem,type,func){ //兼容IE
          if(elem.addEventListener){
            elem.addEventListener(type,func,false)
          }else if(elem.attachEvent){
            elem.attachEvent('on'+type,func)
          }
        }
        function getIndex(event) { //兼容IE
          var e = event || window.event;
          var t = e.target || e.srcElement;
          if (t.tagName.toLowerCase() === 'a') {
            return parseInt(t.innerHTML);
          }
        }
        function showInfo(index,msg){
          var info = gbyId('star-info');
          info.style.display = 'block';
          info.style.left = index*21-51+'px';
          info.innerHTML = "<strong> "+index+'分 '+msg[index-1].match(/(.+)\|/)[1]+'<br />'+'</strong>'+msg[index-1].match(/\|(.+)/)[1];
        }
        function appenStar(elem,nums){
          var frag = document.createDocumentFragment(); //为了提高性能,因使用DocumentFragment一次性append,这样页面只重新渲染一次
          for(var i = 0;i<nums;i++){
            var a =document.createElement('a');
            a.innerHTML = i+1;
            a.href = "javascript:;"; //阻止浏览器的点击链接的默认行为
            frag.appendChild(a);
          }
          elem.appendChild(frag);
        }
        //主体函数
        function star(num,myMsg){
          var n = num||5; //当num有值则取其值,无值则取默认值5;
          var clickStar=curentStar=0; //clickStar保存点击状态
          var msg = myMsg||[
            "很不满意|差得太离谱，与卖家描述的严重不符，非常不满",
            "不满意|部分有破损，与卖家描述的不符，不满意",
            "一般|质量一般，没有卖家描述的那么好",
            "满意|质量不错，与卖家描述的基本一致，还是挺满意的",
            "非常满意|质量非常好，与卖家描述的完全一致，非常满意"
          ];
          var starContainer = gbyId('star-div');
          appenStar(starContainer,n);
          addEvent(starContainer,'mouseover',over); //采用事件代理模式(通过<a>标签的父元素starContainer来代理事件)
          addEvent(starContainer,'mouseout',out);
          addEvent(starContainer,'click',click);
          function over(event){
            if(getIndex(event)){ //若getIndex(event)取不到值,说明当前触发事件的目标不是<a>标签
              var index = getIndex(event);
              change(index);
              showInfo(index,msg);
            }
          }
          function out(event){
            change(); //将评分设为已点击状态clickStar
            gbyId('star-info').style.display = 'none'
          }
          function click(event) {
            if (getIndex(event)) {
              var index = getIndex(event);
              clickStar = index; //保存点击状态
              gbyId('star-info').style.display = 'none';
              gbyId('star-span').innerHTML = "<strong>" + index + '分 ' + msg[index - 1].match(/(.+)\|/)[1] + '</strong>'+'<br />'+ msg[index - 1].match(/\|(.+)/)[1];
            }
          }
          function change(index){
            curentStar = index||clickStar;
            for(var i=0;i<n;i++){
              starContainer.children[i].className = i<curentStar ? 'on' : ''
            }
          }
        }
        return {
          star:star
        }
      }(); //这里的()表示函数立即执行,这样变量sufuStar才能调用匿名函数的返回值star

      //调用执行: sufuStar.star(num,myMsg),参数可为空,参数num,myMsg将设为默认值
      sufuStar.star();
    }
  </script>
</head>
<body>
<div id="star">
  <span>点击星星打分:</span>
  <div id="star-div">
  </div>
  <span id="star-span"></span>
  <p id="star-info">
  </p>
</div>
</body>
</html>