利用Array Prototype的方法来实现对dom集合的筛选、indexOf、map等功能

<!DOCTYPE html><html>
    <head>
        <title>TODO supply a title</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <style type="text/css">
            div{background-color:red;margin:10px;}
        </style>
    </head>
    <body>
        <div class="w50" style="50px;height:20px"></div>
        <div class="w20" style="20px;height:20px"></div>
        <div class="w30" id="test" style="30px;height:20px"></div>
        <div class="w40" style="40px;height:20px"></div>
        <div class="w10" style="10px;height:20px"></div>
    </body>
</html>

var arrPro = Array.prototype;
var core_filter = arrPro.filter;
var core_indexOf = arrPro.indexOf;
var core_slide = arrPro.slice;
var core_sort = arrPro.sort;
var core_map  = arrPro.map;

//当然 为了兼容，应该有toArray方法，对不支持slice.call(nodeList)的浏览器，使用循环
var divArr = core_slide.call(document.getElementsByTagName('div'));

console.log('筛选出所有宽度小于等于30px的div',core_filter.call(divArr,function(item,index){                
    return parseInt(item.style.width,10) <= 30;
}));
console.log('获取#test元素的索引',core_indexOf.call(divArr,document.getElementById('test')));
console.log('按照宽度倒叙排序',core_sort.call(divArr,function(a,b){
    return parseInt(a.style.width,10) < parseInt(b.style.width,10);
}));
//将所有div背景色改为黑色
core_map.call(divArr,function(item){
    item.style.backgroundColor = 'black';
});

firebug截图：