Function extend

m3u8/vue.js:241–246

* Mix properties into target object.

(to, _from)

   * Mix properties into target object.
   */
  function extend (to, _from) {
    for (var key in _from) {
      to[key] = _from[key];
    }
    return to
  }

  /**
   * Merge an Array of Objects into a single Object.