代码：

<script>
    var v1=document.getElementById('my1');
    console.log(v1);

    var v2=document.getElementsByTagName("h2");
    console.log(v2);

    for (var i=0;i<v2.length;i++){
        console.log(v2[i]);
    }

    var v3=document.querySelector("#my1");
    console.log(v3);

    var v4=document.querySelectorAll('h1');
    console.log(v4[0]);
    console.log(v4[1]);
</script>

 

后