{"action":"opened","issue":{"url":"https://api.github.com/repos/facebook/react/issues/4163","labels_url":"https://api.github.com/repos/facebook/react/issues/4163/labels{/name}","comments_url":"https://api.github.com/repos/facebook/react/issues/4163/comments","events_url":"https://api.github.com/repos/facebook/react/issues/4163/events","html_url":"https://github.com/facebook/react/issues/4163","id":89189898,"number":4163,"title":"isMounted() returning undefined","user":{"login":"chandu0101","id":2179670,"avatar_url":"https://avatars.githubusercontent.com/u/2179670?v=3","gravatar_id":"","url":"https://api.github.com/users/chandu0101","html_url":"https://github.com/chandu0101","followers_url":"https://api.github.com/users/chandu0101/followers","following_url":"https://api.github.com/users/chandu0101/following{/other_user}","gists_url":"https://api.github.com/users/chandu0101/gists{/gist_id}","starred_url":"https://api.github.com/users/chandu0101/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/chandu0101/subscriptions","organizations_url":"https://api.github.com/users/chandu0101/orgs","repos_url":"https://api.github.com/users/chandu0101/repos","events_url":"https://api.github.com/users/chandu0101/events{/privacy}","received_events_url":"https://api.github.com/users/chandu0101/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-06-18T03:46:20Z","updated_at":"2015-06-18T03:46:20Z","closed_at":null,"body":"isMounted() returning undefined instead of false/true\r\n\r\n```js\r\n\r\n   * Checks whether or not this composite component is mounted.\r\n       * @return {boolean} True if mounted, false otherwise.\r\n       * @protected\r\n       * @final\r\n       */\r\n      isMounted: function() {\r\n        if (\"production\" !== process.env.NODE_ENV) {\r\n          var owner = ReactCurrentOwner.current;\r\n          if (owner !== null) {\r\n            (\"production\" !== process.env.NODE_ENV ? warning(\r\n              owner._warnedAboutRefsInRender,\r\n              '%s is accessing isMounted inside its render() function. ' +\r\n              'render() should be a pure function of props and state. It should ' +\r\n              'never access something that requires stale data from the previous ' +\r\n              'render, such as refs. Move this logic to componentDidMount and ' +\r\n              'componentDidUpdate instead.',\r\n              owner.getName() || 'A component'\r\n            ) : null);\r\n            owner._warnedAboutRefsInRender = true;\r\n          }\r\n        }\r\n        var internalInstance = ReactInstanceMap.get(this); // undefined in our case\r\n        return (\r\n          internalInstance &&\r\n          internalInstance !== ReactLifeCycle.currentlyMountingInstance\r\n        );\r\n      },\r\n\r\n```\r\nplease check this for long story : https://github.com/japgolly/scalajs-react/pull/146#issuecomment-112982975"}}