- To use state hook you serve the state but what about life cycle methods? How do we hack into the life cycle methods like ComponentDidMount, ComponentDidUpdate and ComponentWillUnmout. These life cycle methods often perform side effects that update stating component and make request for data. Step up the effect hook use effect. This effectively replaces all three of those life cycle methods in one call back function. The use effect hook runs after React flushes changes to the DOM after every render, including after the initial one. It takes an argument of a callback function to execute when use effect is run and optionally an array of dependencies for the effect. We will come back to this array later. We declare use effect inside the component's function body so it and it's callback both have access to components props and state. The use effect callback can update state by calling the state update functions the main body of the callback function replaces ComponentDidMount and ComponentDidUpdate life cycle methods founding class components. Clean up is also performed by the use effect hook by adding a return to it's callback. The return itself should be a callback that performs a required tasks. We can have more than one effect hook in a component.