Convert returned JSON Object Properties to (lower first) camelCase

I have JSON returned from an API like so:

Contacts: [{ GivenName: "Matt", FamilyName:"Berry" }]

To keep this consitent with my code style (camelCase - lower case first letter) I want to transform the array to produce the following:

 contacts: [{ givenName: "Matt", familyName:"Berry" }]

Whats the easiest/best way to do this? create a new Contact object and iterate over all the conatacts in the returned array?

I needed a generic method that accepted an array or object. This is what I'm using (I borrowed KyorCode's firstToLower() implementation):

function convertKeysToCamelCase(obj) {
    if (!obj || typeof obj !== "object") return null;

    if (obj instanceof Array) {
        return $.map(obj, function(value) {
            return convertKeysToCamelCase(value);
        });
    }

    var newObj = {};
    $.each(obj, function(key, value) {
        key = key.charAt(0).toLowerCase() + key.slice(1);
        newObj[key] = value;
    });

    return newObj;
};

Example calls:

var contact = { GivenName: "Matt", FamilyName:"Berry" };

console.log(convertKeysToCamelCase(contact));
// logs: Object { givenName="Matt", familyName="Berry"}

console.log(convertKeysToCamelCase([contact]));
// logs: [Object { givenName="Matt", familyName="Berry"}]

console.log(convertKeysToCamelCase("string"));
// logs: null

console.log(contact);
// logs: Object { GivenName="Matt", FamilyName="Berry"}