machinecat520
/
zj-Exercise


			
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							<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button>测试1</button>
    <button>测试2</button>
    <button>测试3</button>
    <!-- 
        需求：点击某个按钮，提示“点击的是第n个按钮”
     -->
    <script>
        var btns = document.getElementsByTagName('button')
        //遍历加监听
        //  for(var i = 0 ,length = btns.length ; i < length ; i++){
        //      var btn = btns[i]
        //      btn.onclick = function(){
        //          alert('点击的是第'+(i+1)+'个按钮')
        //      }
        //  }

        // for (var i = 0, length = btns.length; i < length; i++) {
        //     var btn = btns[i]
        //     //将btn所对应的下标保存在btn上
        //     btn.index = i
        //     btn.onclick = function () {
        //         alert('点击的是第' + (this.index + 1) + '个按钮')
        //     }
        // }

        //利用闭包
        for (var i = 0, length = btns.length; i < length; i++) {
            (function(i){
                var btn = btns[i]
                btn.onclick = function(){
                    alert('点击的是第'+(i+1)+'个按钮')
                }
            })(i)
        }


    </script>
</body>

</html>