How do I indicate that a checkbox should be checked?

[andersond]

I have a form named "FrontPage_Form 2" and a checkbox named "checkboxPowerU nit"; and, I want to programmaticall y change whether or not it is checked by default based on a selection made in a selection box. I have tried:

document.FrontPage_Form2.checkboxPowerUnit.checked=true;
document.all.checkboxPowerUnit.checked=true;
document.form[0].checkboxPowerUnit.checked=true;
document.form[0].checkboxPowerUnit[0].checked=true;
document.FrontPage_Form2].checkboxPowerUnit[0].checked=true;

and every one results in an error saying "document.whate ver" is null or not an object. Can anyone tell me how to indicate that this checkbox should be checked or unchecked?

[Plater]

Assign it an id and then use document.getEle mentById(idstri ng)

[andersond]

it has an id. the id and the name are the same.

[andersond]

document.getElementById('checkboxPowerUnit').checked=true;
document.getElementById('checkboxPowerUnit').value="YES";

also do not work

[Plater]

Are you perhaps running this script before the page has loaded?
if document.getEle mentById('check boxPowerUnit') is giving you a null object, then that object does not exist

http://www.w3schools.com/JS/tryit.asp?filename=try_dom_input_checked