whole_func_string: function defaults(dst, src) {
    forEach(src, function(value, key) {
      if (!isDefined(dst[key])) {
        dst[key] = value;
      }
    });
  }
func_code_string: function defaults(dst, src) {
    forEach(src, function(value, key) {
      if (!isDefined(dst[key])) {
        dst[key] = value;
      }
    });
  }
func_documentation_string: shallow copy over values from `src` that are not already specified on `dst`