react app

react-app/node_modules/react/lib/ReactTransitionChildMapping.js

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+/**
+ * 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;