Hello, I've got 2 radio button groups showed differently depending on the value selected on another radio button. The thing is that I would like to set the default value of the group to the first element in the radiobutton group, but when I change from the other radio button it preserves the value previously selected, when I want it to be reset to the default value.

I've been searching in the javascript repository but apparently I cannot access like it says with radio[1].checked = true... It says that radio[1] is undefined, but radio is an HTML Input element object. I'm accessing it from a different file, but var radio = document.getElementById("radio") works, but I can't access the individual radiobuttons.

Thank you in advance