export function extend(obj) {
    var arg, i, k;

    for (i = 1; i < arguments.length; i++) {
        arg = arguments[i];

        for (k in arg) {
            if (arg.hasOwnProperty(k)) {
                obj[k] = arg[k];
            }
        }
    }

    return obj;
};

export function extend(obj) {
    var arg, i, k;

    for (i = 1; i < arguments.length; i++) {
        arg = arguments[i];

        for (k in arg) {
            if (arg.hasOwnProperty(k) && arg[k] !== undefined) {
                obj[k] = arg[k];
            }
        }
    }

    return obj;
}

Update extend to not carry over undefined values.
feat(extend): Update extend to not carry over undefined values.
