updated #7. pure functional component info

README.md

@@ -513,7 +513,7 @@ You can download the PDF and Epub version of this repository from the latest run
 
 7. ### What are Pure Components?
 
-    *`React.PureComponent`* is exactly the same as *`React.Component`* except that it handles the `shouldComponentUpdate()` method for you. When props or state changes, *PureComponent* will do a shallow comparison on both props and state. *Component* on the other hand won't compare current props and state to next out of the box. Thus, the component will re-render by default whenever `shouldComponentUpdate` is called.
+    *`React.PureComponent`* is exactly the same as *`React.Component`* except that it handles the `shouldComponentUpdate()` method for you. When props or state changes, *PureComponent* will do a shallow comparison on both props and state. *Component* on the other hand won't compare current props and state to next out of the box. Thus, the component will re-render by default whenever `shouldComponentUpdate` is called. In functional componenets we use `React.memo()` API. `React.memo()` is a higher-order component. It takes a React component as its first argument and returns a special type of React component that allows the renderer to render the component while memoizing the output. Therefore, if the component’s props are shallowly equal, the `React.memo()` component will bail out the updates.
 
 
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