react/src/utils/cloneWithProps.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.
 *
 * @typechecks
 * @providesModule cloneWithProps
 */

"use strict";

var ReactElement = require('ReactElement');
var ReactPropTransferer = require('ReactPropTransferer');

var keyOf = require('keyOf');
var warning = require('warning');

var CHILDREN_PROP = keyOf({children: null});

/**
 * Sometimes you want to change the props of a child passed to you. Usually
 * this is to add a CSS class.
 *
 * @param {object} child child component you'd like to clone
 * @param {object} props props you'd like to modify. className and style will be
 * merged automatically.
 * @return {object} a clone of child with props merged in.
 */
function cloneWithProps(child, props) {
  if (__DEV__) {
    warning(
      !child.ref,
      'You are calling cloneWithProps() on a child with a ref. This is ' +
      'dangerous because you\'re creating a new child which will not be ' +
      'added as a ref to its parent.'
    );
  }

  var newProps = ReactPropTransferer.mergeProps(props, child.props);

  // Use `child.props.children` if it is provided.
  if (!newProps.hasOwnProperty(CHILDREN_PROP) &&
      child.props.hasOwnProperty(CHILDREN_PROP)) {
    newProps.children = child.props.children;
  }

  // The current API doesn't retain _owner and _context, which is why this
  // doesn't use ReactElement.cloneAndReplaceProps.
  return ReactElement.createElement(child.type, newProps);
}

module.exports = cloneWithProps;