What are the methods for accessing node objects in JavaScript and how to use them_javascript tips

JavaScript中访问节点对象的方法有哪些？

复制代码 代码如下:

var obj = document.getElementById('fdafda');

var obj = document.f1;
obj.method="post";
obj.action='Bb';

var obj = document.f1.userName;

var obj = document.forms[0].userName;

var obj = document.forms[0].elements[0];

var obj = document.f1.elements[0];
var obj = document.forms["f1"].elements["userName"];
var obj = document.forms[0].like;
for(var i=0;i{
var aa = obj[i];
if(aa.checked)
{
alert();
}
}