code: function applyKey(config, keyPath, value) {
      var currentKey;
  
      if (Array.isArray(keyPath)) {
          if (config[keyPath[0]] === undefined) { // eslint-disable-line no-undefined
              return;
          }
  
          currentKey = keyPath.shift();
  
          if (keyPath.length === 0) {
              config[currentKey] = value;
              return;
          }
  
          applyKey(config[currentKey], keyPath, value);
      }
  }
docs: Set <value> for <keyPath> on <config>.
  
  @param {Object} config
  @param {Array|string} keyPath
  @param {*} value