consult and doubt Javascript Best Practices number 5

[Manuel Jordan]

Hello guys
(sorry for my grammar)

The motive of this is a consult, i dont have a high knowledge about js, only the necessary

i saw this link http://www.javascripttoolbox.com/bestpractices/ number 5

the doubt and consult is the next
when i have a simple "form" with N fields and the "form" declared in this way

<form name="insertWorker" action="insertWorker" focus="somefield"  onsubmit="return ValidationForm()">

where the method ValidationForm() is defined and included how an external file like

<script type="text/javascript" src="path..../workervalidationform.js"></script>

i saw in the mentionated link the suggestion 5 "Reference Forms and Form Elements Correctly"

so i apply now in my code the mentioaned suggestion

function ValidarFormulario(){
 
 //checkform=document.insertWorker;//my bad way
 var checkform=document.forms["insertWorker"].elements;
 var state=true;
 
 //zone of nulls
 //formElements["input1"].value="a"; GOOD
 //checkform.nombresObrero.value= BAD
 if(checkform["codigoObrero"].value==""){
    checkform["codigoObrero"].style.color="#2F4F4F";
    checkform["codigoObrero"].style.backgroundColor='#A9A9A9';
    state=false;
 }
 if(checkform["apellidosObrero"].value==""){
    checkform["apellidosObrero"].style.color="#2F4F4F";
    checkform["apellidosObrero"].style.backgroundColor='#A9A9A9';
    state=false;
 }
more validations....

my really doubt is when i should use getElementById("someid") and
formElements["namefield"] like the way mentionated

maybe the question is silly, but i saw in others pages of the Web that not use
the way suggested (use or work with my wrong way), so i am confused

but i know by a good reference that is necessary and is a good practice
and maybe a rule of gold work with getElementById
(see http://www.mozilla.org/docs/web-developer/upgrade_2.html )
to access an element in a html page

so which and when i should use the suggested way and getElementById

i am not an expert in javascript

please help to resolve my doubt

thanks so much for advanced
[ November 10, 2006: Message edited by: Manuel Jordan ]