react app

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

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+/**
+ * Copyright 2014-2015, 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.
+ *
+ * @providesModule ReactChildReconciler
+ * @typechecks static-only
+ */
+
+'use strict';
+
+var ReactReconciler = require("./ReactReconciler");
+
+var flattenChildren = require("./flattenChildren");
+var instantiateReactComponent = require("./instantiateReactComponent");
+var shouldUpdateReactComponent = require("./shouldUpdateReactComponent");
+
+/**
+ * ReactChildReconciler provides helpers for initializing or updating a set of
+ * children. Its output is suitable for passing it onto ReactMultiChild which
+ * does diffed reordering and insertion.
+ */
+var ReactChildReconciler = {
+
+  /**
+   * Generates a "mount image" for each of the supplied children. In the case
+   * of `ReactDOMComponent`, a mount image is a string of markup.
+   *
+   * @param {?object} nestedChildNodes Nested child maps.
+   * @return {?object} A set of child instances.
+   * @internal
+   */
+  instantiateChildren: function(nestedChildNodes, transaction, context) {
+    var children = flattenChildren(nestedChildNodes);
+    for (var name in children) {
+      if (children.hasOwnProperty(name)) {
+        var child = children[name];
+        // The rendered children must be turned into instances as they're
+        // mounted.
+        var childInstance = instantiateReactComponent(child, null);
+        children[name] = childInstance;
+      }
+    }
+    return children;
+  },
+
+  /**
+   * Updates the rendered children and returns a new set of children.
+   *
+   * @param {?object} prevChildren Previously initialized set of children.
+   * @param {?object} nextNestedChildNodes Nested child maps.
+   * @param {ReactReconcileTransaction} transaction
+   * @param {object} context
+   * @return {?object} A new set of child instances.
+   * @internal
+   */
+  updateChildren: function(
+    prevChildren,
+    nextNestedChildNodes,
+    transaction,
+    context) {
+    // We currently don't have a way to track moves here but if we use iterators
+    // instead of for..in we can zip the iterators and check if an item has
+    // moved.
+    // TODO: If nothing has changed, return the prevChildren object so that we
+    // can quickly bailout if nothing has changed.
+    var nextChildren = flattenChildren(nextNestedChildNodes);
+    if (!nextChildren && !prevChildren) {
+      return null;
+    }
+    var name;
+    for (name in nextChildren) {
+      if (!nextChildren.hasOwnProperty(name)) {
+        continue;
+      }
+      var prevChild = prevChildren && prevChildren[name];
+      var prevElement = prevChild && prevChild._currentElement;
+      var nextElement = nextChildren[name];
+      if (shouldUpdateReactComponent(prevElement, nextElement)) {
+        ReactReconciler.receiveComponent(
+          prevChild, nextElement, transaction, context
+        );
+        nextChildren[name] = prevChild;
+      } else {
+        if (prevChild) {
+          ReactReconciler.unmountComponent(prevChild, name);
+        }
+        // The child must be instantiated before it's mounted.
+        var nextChildInstance = instantiateReactComponent(
+          nextElement,
+          null
+        );
+        nextChildren[name] = nextChildInstance;
+      }
+    }
+    // Unmount children that are no longer present.
+    for (name in prevChildren) {
+      if (prevChildren.hasOwnProperty(name) &&
+          !(nextChildren && nextChildren.hasOwnProperty(name))) {
+        ReactReconciler.unmountComponent(prevChildren[name]);
+      }
+    }
+    return nextChildren;
+  },
+
+  /**
+   * Unmounts all rendered children. This should be used to clean up children
+   * when this component is unmounted.
+   *
+   * @param {?object} renderedChildren Previously initialized set of children.
+   * @internal
+   */
+  unmountChildren: function(renderedChildren) {
+    for (var name in renderedChildren) {
+      var renderedChild = renderedChildren[name];
+      ReactReconciler.unmountComponent(renderedChild);
+    }
+  }
+
+};
+
+module.exports = ReactChildReconciler;