code: function executeSelector(source, sourceKey, targetKey,
          sourceKeys, overrideKeys) {
  
          for (var prefix in selectors) {
              // sourceKey starts with selector's prefix
              if (sourceKey.indexOf(prefix) === 0) {
  
                  // Remove prefix from source key.
                  sourceKey = sourceKey.substring(prefix.length);
  
                  // Execute the selector's handler.
                  selectors[prefix]({
                      source: source,
                      sourceKey: sourceKey,
                      targetKey: targetKey ? targetKey : sourceKey,
                      sourceKeys: sourceKeys,
                      overrideKeys: overrideKeys
                  });
  
                  return true;
              }
          }
          return false;
      }
docs: /*
  Checks whether the source key matches one of the existing selectors.
  If it does, the selector's handler is invoked on the source key.
  
  @param {object} source The source object.
  @param {string} sourceKey The source object key.
  @param {string} targetKey The target object key.
  @param {object} sourceKeys The keys of the source properties to merge.
  @param {object} overrideKeys
  The keys of the source properties to not report an error if the
  property already exists in the target object.