@react-md/utils/src/defaults.ts

General utils for react-md.

type Rec = Record<string, unknown>;

/**
 * This is normally used for reusable shareable configs that have multiple
 * shared options with default values that should be used. This basically works
 * just like `defaultProps` in react.
 *
 * @internal
 * @param optional - The original object that has the optional/omitted values
 * @param required - The required default values that should be used to fill the
 * optional object with
 * @returns a new object with both the values of the optional and required
 * objects but use the optional values if they were defined.
 */
export function defaults<O extends {}, R extends {}>(
  optional: O,
  required: R
): O & R {
  const keys = Object.keys(required);

  return keys.reduce<O & R>(
    (result, key) => {
      if (typeof (result as Rec)[key] === "undefined") {
        (result as Rec)[key] = (required as Rec)[key];
      }

      return result;
    },
    { ...optional } as O & R
  );
}