define(['../array/forEach', '../array/slice', './forOwn'], function (forEach, slice, forOwn) {

    /**
     * Copy missing properties in the obj from the defaults.
     */
    function fillIn(obj, var_defaults){
        forEach(slice(arguments, 1), function(base){
            forOwn(base, function(val, key){
                if (obj[key] == null) {
                    obj[key] = val;
                }
            });
        });
        return obj;
    }

    return fillIn;

});