Need explanation of how script is working

[evergrean100]

This below validates and makes sure all radio buttons are populated on web page. I dont understand how it works and was hoping to get explanation:

function val(){
var myForm=document.getElementById("myForm");
var myFields=myForm.getElementsByTagName("input");
var results={};
var resultString="";
	
for (var i=0;i<myFields.length;i++) {
if(myFields[i].type=="radio"){
//The next two lines are the main areas I need expanation because not sure why it checking "undefined" and then naming it 0? 
if(results[myFields[i].name]==undefined) results[myFields[i].name]=0;
//What is being iterated here and why?
if(myFields[i].checked) results[myFields[i].name]++;
}
}

//I never seen a for loop statment saying for(fieldName in results)...Is this new syntax and what is it equivalent to??	
for(fieldName in results)if(results[fieldName]==0) resultString+= " "+fieldName;

if(resultString!="") alert("Fields are required, but missing:\n"+resultString);
}

 

[ggriffit]

try this long hand version :

function val(){
var myForm=document.getElementById("myForm");
var myFields=myForm.getElementsByTagName("input");
var results={};
var resultString="";

for (var i=0;i<myFields.length;i++)
{
if(myFields.type=="radio")
{
if(results[myFields.name]==undefined)
{
results[myFields.name]=0;
}

if(myFields.checked)
{
results[myFields.name]++;
}
}
}

for(fieldName in results)
{
if(results[fieldName]==0)
{
resultString+= " "+fieldName;
}
if(resultString!="")
{
alert("Fields are required, but missing:\n"+resultString);
}
}

Greg Griffiths
Livelink Certified Developer & ECM Global Star Champion 2005

http://www.greggriffiths.org/livelink/