I want add this to my checkbox: validate="required:true". It results in this:

```
<input type="radio" name="persoonskamer" value="Ja" validate="required:true">

```

But now i have a problem. I used a form cms generator. In my cms, i can not add this direct to the html. I can only give the input a classes. How can i add "validate="required:true" that to my input with javascript.

Thanks for you help guys!