Set read only check box

[ghjk]

I want to set read only for check box when I click submit button. But my code didn't work. This is my code java script code.

document.getElementsById('check')[0].disabled=true;
document.getElementsById('check')[1].disabled=true;
or 
document.getElementById('check')[0].readOnly=true;
document.getElementById('check')[1].readOnly=true;

could someone help me? I'm using php and javascript.

[Dormilich]

document.getElementsById('check')[0]

should be undefined. getElementsById () is an invalid method call.

[acoder]

...and

document.getElementById('check')[0]

doesn't make sense because it returns a single element. You need to give your elements unique IDs or access them by name.

[Dormilich]

...and

document.getElementById('check')[0]

doesn't make sense because it returns a single element.

additional info: that call would look for the property "0" of the element with the id "check" and because Elements usually* don’t have such a property, undefined is returned.

* except when you explicity define such a property