Izmjenjena struktura, dodan backand

web/node_modules/react/lib/onlyChild.js

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+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+'use strict';
+
+var _prodInvariant = require('./reactProdInvariant');
+
+var ReactElement = require('./ReactElement');
+
+var invariant = require('fbjs/lib/invariant');
+
+/**
+ * Returns the first child in a collection of children and verifies that there
+ * is only one child in the collection.
+ *
+ * See https://facebook.github.io/react/docs/top-level-api.html#react.children.only
+ *
+ * The current implementation of this function assumes that a single child gets
+ * passed without a wrapper, but the purpose of this helper function is to
+ * abstract away the particular structure of children.
+ *
+ * @param {?object} children Child collection structure.
+ * @return {ReactElement} The first and only `ReactElement` contained in the
+ * structure.
+ */
+function onlyChild(children) {
+  !ReactElement.isValidElement(children) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'React.Children.only expected to receive a single React element child.') : _prodInvariant('143') : void 0;
+  return children;
+}
+
+module.exports = onlyChild;