listOrArray.js

function listOrArray(Arr) {
    var List = Array.prototype.slice.call(arguments, 1),
        i;

    // If `List` is not empty, assume there are more module objects sent as List Arguments
    if (List.length > 0) {
        List.unshift(Arr);
        Arr = List;
    } else {
        // No List args in sight, treat the first arg `Arr` as an array and loop through it.
        // Even if there's just one.
        Arr = [].concat(Arr);
    }

    // Loop through that array
    for (i in Arr) {
        if (Arr.hasOwnProperty(i)) {
            // Do something
        }
    }
}

use.md

List or Array

This function can take multiple arguments, either as a List or an Array.

listOrArray(1, 2, 3);// List
listOrArray(["a", "b", "c"]);// Array