Updating phase in React - Cheat Sheet & Quick Revision

Recall & Review

beginner

What triggers the updating phase in a React component?

The updating phase happens when a component's state or props change, causing React to re-render the component to reflect new data.

beginner

Which React hook is commonly used to perform side effects during the updating phase?

useEffect hook runs after rendering and is used to perform side effects like fetching data or updating the DOM during the updating phase.

beginner

What is the role of the useState hook in the updating phase?

useState lets you add state to a functional component. When you update this state, React triggers the updating phase to re-render the component with new values.

intermediate

How does React decide whether to re-render a component during the updating phase?

React compares the new props and state with the previous ones. If they differ, React re-renders the component to update the UI.

beginner

What is the difference between the initial render and the updating phase in React?

The initial render happens when the component first appears on screen. The updating phase happens later when props or state change, causing React to update the component's output.

What causes React to enter the updating phase?

A When the component is first created

B When the browser window resizes

C A change in component state or props

D When the user clicks anywhere on the page

React updates a component when its state or props change, triggering the updating phase.

Which hook runs after every render during the updating phase?

A useEffect

B useState

C useRef

D useMemo

useEffect runs after rendering and is used for side effects during updates.

What happens if React detects no change in props or state during an update?

A It crashes the app

B It skips re-rendering the component

C It forces a re-render anyway

D It reloads the entire page

React optimizes performance by skipping re-render if props and state are unchanged.

Which of these is NOT part of the updating phase?

A Initial mounting of the component

B Comparing new and old props/state

C Calling <code>useEffect</code> after render

D Re-rendering the component

Initial mounting is the first render, not part of the updating phase.

How can you trigger the updating phase manually in a functional component?

A By changing the HTML file

B By refreshing the browser

C By calling <code>useEffect</code> directly

D By calling <code>setState</code> or the updater from <code>useState</code>

Updating state with the updater function from useState triggers the updating phase.

Explain what happens during the updating phase in React and how state changes affect it.

Think about what causes React to update and what happens after.

Describe how the useState hook is involved in the updating phase of a React component.

Focus on how changing state affects rendering.