setAttribute(要获取的属性，属性值)
    获取元素属性

    1.     <img src="" alt="">
    2.     <script>
    3.         var img = document.querySelector('img');
    4.         img.setAttribute('src','./1.jpg')

    window.getComputedStyle
    可以获取计算过后的css属性值，使用style获取的是行间样式
    image.png
    currentStyle
    ie独有

    1. <head>
    2.     <meta charset="UTF-8">
    3.     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    4.     <title>Document</title>
    5.     <style>
    6.         .move{
    7.             width: 100px;
    8.             height: 100px;
    9.             position: absolute;
    10.             background: red;
    11.             opacity: 0.5;
    12.         }
    13.     </style>
    14. </head>
    15. <body>
    16.     <div class="move"></div>
    17.     <script>
    18.         var div = document.getElementsByClassName('move')[0];
    19.         function getStyle(dom,attr){
    20.             if(window.getComputedStyle){
    21.                 return window.getComputedStyle(dom,null)[attr];
    22.             }else{
    23.                 return dom.currentStyle[attr];
    24.             }
    25.         }
    26.         console.log(getStyle(div,'opacity'))
    27.     </script>
    28. </body>