WIP - add extractor, generate snippet_data

node_modules/fbjs/lib/ExecutionEnvironment.js.flow

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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.
+ *
+ * @providesModule ExecutionEnvironment
+ */
+'use strict';
+
+const canUseDOM = !!(typeof window !== 'undefined' && window.document && window.document.createElement);
+/**
+ * Simple, lightweight module assisting with the detection and context of
+ * Worker. Helps avoid circular dependencies and allows code to reason about
+ * whether or not they are in a Worker, even if they never include the main
+ * `ReactWorker` dependency.
+ */
+
+const ExecutionEnvironment = {
+  canUseDOM: canUseDOM,
+  canUseWorkers: typeof Worker !== 'undefined',
+  canUseEventListeners: canUseDOM && !!(window.addEventListener || window.attachEvent),
+  canUseViewport: canUseDOM && !!window.screen,
+  isInWorker: !canUseDOM // For now, this is true - might change in the future.
+
+};
+module.exports = ExecutionEnvironment;