Method extend

src/extras/primitives/primitives.js:117–128

* For the base to be extensible, both objects must be pure JavaScript objects. * The function assumes that base is undefined, or null or a pure object.

(base, extension)

       * The function assumes that base is undefined, or null or a pure object.
       */
      function extend (base, extension) {
        if (isUndefined(base)) {
          return copy(extension);
        }
        if (isUndefined(extension)) {
          return copy(base);
        }
        if (isPureObject(base) && isPureObject(extension)) {
          return utils.extendDeep(base, extension);
        }
        return copy(extension);
      }

      function isUndefined (value) {
        return typeof value === 'undefined';