Question

This is surely a JS beginner question.

My issue is I want to use the value of the variable type to access the relevant checkbox; however it is treating the variable as a string. I have tried it to two ways.

function toggleGroup(type) {
    if (document.getElementById(type).checked == true){
        alert("foo");
    }
}

or

function toggleGroup(type) {
    if (document.nav.type.checked == true){
        alert("foo");           
    }
}

Answer 1

We have no way of knowing how type should be treated – you haven’t show us how the function is being called (in particular, we don’t know what you are passing as its argument).

If it is a string (matching the id of an element), than document.getElementById(type).checked should work (although == true is redundant).

document.nav.type.checked should not work, because dot-notation property names are not interpolated. You have to use square bracket notation for that: document.forms.nav.elements[type].checked. This will match on name or id – if you have multiple elements with the same name, then document.forms.nav.elements[type] will be an object you can treat as an array (and won’t have a checked property).