/** * Copyright 2013-2015, 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 static-only * @providesModule ReactTransitionChildMapping */ 'use strict'; var ReactChildren = require("./ReactChildren"); var ReactFragment = require("./ReactFragment"); var ReactTransitionChildMapping = { /** * Given `this.props.children`, return an object mapping key to child. Just * simple syntactic sugar around ReactChildren.map(). * * @param {*} children `this.props.children` * @return {object} Mapping of key to child */ getChildMapping: function(children) { if (!children) { return children; } return ReactFragment.extract(ReactChildren.map(children, function(child) { return child; })); }, /** * When you're adding or removing children some may be added or removed in the * same render pass. We want to show *both* since we want to simultaneously * animate elements in and out. This function takes a previous set of keys * and a new set of keys and merges them with its best guess of the correct * ordering. In the future we may expose some of the utilities in * ReactMultiChild to make this easy, but for now React itself does not * directly have this concept of the union of prevChildren and nextChildren * so we implement it here. * * @param {object} prev prev children as returned from * `ReactTransitionChildMapping.getChildMapping()`. * @param {object} next next children as returned from * `ReactTransitionChildMapping.getChildMapping()`. * @return {object} a key set that contains all keys in `prev` and all keys * in `next` in a reasonable order. */ mergeChildMappings: function(prev, next) { prev = prev || {}; next = next || {}; function getValueForKey(key) { if (next.hasOwnProperty(key)) { return next[key]; } else { return prev[key]; } } // For each key of `next`, the list of keys to insert before that key in // the combined list var nextKeysPending = {}; var pendingKeys = []; for (var prevKey in prev) { if (next.hasOwnProperty(prevKey)) { if (pendingKeys.length) { nextKeysPending[prevKey] = pendingKeys; pendingKeys = []; } } else { pendingKeys.push(prevKey); } } var i; var childMapping = {}; for (var nextKey in next) { if (nextKeysPending.hasOwnProperty(nextKey)) { for (i = 0; i < nextKeysPending[nextKey].length; i++) { var pendingNextKey = nextKeysPending[nextKey][i]; childMapping[nextKeysPending[nextKey][i]] = getValueForKey( pendingNextKey ); } } childMapping[nextKey] = getValueForKey(nextKey); } // Finally, add the keys which didn't appear before any key in `next` for (i = 0; i < pendingKeys.length; i++) { childMapping[pendingKeys[i]] = getValueForKey(pendingKeys[i]); } return childMapping; } }; module.exports = ReactTransitionChildMapping;