HTML索引有什么举例吗？

var infoMsg = new Object();
infoMsg.firstname=document.getElementByld("firstname").value
......
var phone =new Object();
var phoneType1=document.getElementByld("phoneType1").
options[document.getElementByld("phoneType1").selectedIndex].text;
var phoneNumber1=document.getElementByld("phoneNumber1").value; 
phone[phoneType1]=phoneNumber1;
var phoneType2=document.getElementByld("phoneType2")
options[document.getElementByld("phoneType2").selectedIndex].text;
var phoneNumber2=document.getElementByld("phoneNumber2").value; phone[phoneType2]=phoneNumber2;
infoMsg.phoneNumbers=phone;
var jsonstr=JSON.stringify(infoMsg);
xmlHttpRequest.open("POST","JsonServlet",true);
xmlHttpRequest.setRequestHeader("Content-type""application/x-www-form-urlencoded"); xmlHttpRequest.onreadystatechange=ajaxCall; 
xmlHttpRequest.send("content="+jsonstr);
console += "Sent: " + isonstr + "\n";