shouldUpdateReactComponent.js

/**
 * Copyright 2013-2014, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule shouldUpdateReactComponent
 * @typechecks static-only
 */

"use strict";

var ReactNativeComponent = require('ReactNativeComponent');

/**
 * Given a `prevElement` and `nextElement`, determines if the existing
 * instance should be updated as opposed to being destroyed or replaced by a new
 * instance. Both arguments are elements. This ensures that this logic can
 * operate on stateless trees without any backing instance.
 *
 * @param {?object} prevElement
 * @param {?object} nextElement
 * @return {boolean} True if the existing instance should be updated.
 * @protected
 */
function shouldUpdateReactComponent(prevElement, nextElement) {
  if (prevElement != null && nextElement != null) {
    var prevType = typeof prevElement;
    var nextType = typeof nextElement;
    if (prevType === 'string' || prevType === 'number') {
      return (nextType === 'string' || nextType === 'number');
    } else {
      return (
        nextType === 'object' &&
        prevElement.type === nextElement.type &&
        prevElement.key === nextElement.key &&
        prevElement._owner === nextElement._owner
      );
    }
  }
  return false;
}

module.exports = shouldUpdateReactComponent;