javascript当中绑定事件和方法

8.绑定事件和方法

马克-to-win：once, long time to know that "script" must be put in behind, while "input" must be put in front,
otherwise document.getElementById("button1"); can not find the "button1"，alert("button1 is "+ button1); 结果就是null，为什么这次跟往常我们的印象不一样了呢？因为往常我们先写一段script，之后在body中写上诸如<INPUT TYPE="button" οnclick="abc",之类的话，这样上面的abc这样的代码开始不会被执行，里面的诸如document.getElementById ("button1");也就正确了。这里为什么跟往常不一样呢？因为要在一开始时，先给button绑上事件代码，否则button无事件响应。

例 8.1（commonEventPrerequisiteIEFF.html）

<head>
    <meta http-equiv="content-type" content="text/html; charset=utf-8"/>
</head>
<INPUT TYPE="button" NAME="button1" ID="button1" VALUE="单击我"/>
<script>
    function testie()
    {
        alert("单击按钮ie");
    }
    function testFF()
    {
        alert("单击按钮FireFox");
    }

        /**/
        /*obj.addEventListener("click",function(){func("看到我了吧");},false);
the third argument is: A Boolean flag value that indicates whether the event listener should
use bubbling (由里向外) or capture (由外向里) event propagation. 只要我们
知道第三个参数和事件冒泡有关就可以了。缺省值为假，即冒泡的意思。具体例子参考后面的事件冒泡例子。
     */
        var button1 = window.document.getElementById("button1");
        alert("button1 is "+ button1);
        alert("document.all is" + document.all);
        alert(typeof(window.addEventListener) + " is typeof window.addEventListener");
        alert(typeof(window.attachEvent) + " is typeof window.attachEvent");
        alert(window.addEventListener + " is window.addEventListener");
        alert(window.attachEvent + " is window.attachEvent");
        if (typeof window.attachEvent === "object")
        {
            alert("ie");
            button1.attachEvent("onclick", testie);
        }
        if (typeof window.addEventListener === "function")
        {
            alert("firefox");
            button1.addEventListener("click", testFF, false);
        }
       // button1.addEventListener("click",test,false);
        //button1.attachEvent("onclick" , test);
        var str = "";

</script>

更多内容请见原文，文章转载自：https://blog.csdn.net/qq_43650923/article/details/102210095