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Primary Reason for Depreciating Lifecycle Hooks in React 16


Primary Reason for Depreciating Lifecycle Hooks in React 16

By : KMToney09
Date : November 20 2020, 07:00 PM
it fixes the issue Because React is implementing async rendering, this will cause lifecycle events like componentWillMount to be called more than once in some cases, that's why the React team is deprecating those methods and marking them as UNSAFE.
You can have some more details in this link.
code :


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React Lifecycle Hooks

React Lifecycle Hooks


By : François Racine
Date : March 29 2020, 07:55 AM
hop of those help? DO NOT make http calls in render method ! You can do that in c̶o̶m̶p̶o̶n̶e̶n̶t̶W̶i̶l̶l̶M̶o̶u̶n̶t̶ componentDidMount for example and set the return values in the state. When you update the state, react will call the render method and redraw your component.
What are the lifecycle hooks in React? When they are used?

What are the lifecycle hooks in React? When they are used?


By : Rafasis
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Lifecycle in React usually refers to the lifecycle of a component, it's expressively portrayed on this diagram (React 16.4):
How to use lifecycle methods with hooks in React?

How to use lifecycle methods with hooks in React?


By : brandjas
Date : March 29 2020, 07:55 AM
around this issue Here are examples for the most common lifecycles:
componentDidMount
code :
function Example() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    document.title = `You clicked ${count} times`;
  }, []); // Pass an empty array to run only callback on mount only.

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}
function Example() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    document.title = `You clicked ${count} times`;
  }); // No second argument, so run after every render.

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}
function Example() {
  const [count, setCount] = useState(0);

  const firstUpdate = useRef(true);
  useLayoutEffect(() => {
    if (firstUpdate.current) {
      firstUpdate.current = false;
      return;
    }

    console.log('componentDidUpdate');
  });

  return (
    <div>
      <p>componentDidUpdate: {count} times</p>
      <button
        onClick={() => {
          setCount(count + 1);
        }}
      >
        Click Me
      </button>
    </div>
  );
}
function Example() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    // Return a callback in useEffect and it will be called before unmounting.
    return () => {
      console.log('componentWillUnmount!');
    };
  }, []);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}
function Parent({ a, b }) {
  // Only re-rendered if `a` changes:
  const child1 = useMemo(() => <Child1 a={a} />, [a]);
  // Only re-rendered if `b` changes:
  const child2 = useMemo(() => <Child2 b={b} />, [b]);
  return (
    <>
      {child1}
      {child2}
    </>
  )
}
function ScrollView({row}) {
  let [isScrollingDown, setIsScrollingDown] = useState(false);
  let [prevRow, setPrevRow] = useState(null);

  if (row !== prevRow) {
    // Row changed since last render. Update isScrollingDown.
    setIsScrollingDown(prevRow !== null && row > prevRow);
    setPrevRow(row);
  }

  return `Scrolling down: ${isScrollingDown}`;
}
About lifecycle hooks in React

About lifecycle hooks in React


By : user3022628
Date : March 29 2020, 07:55 AM
like below fixes the issue useEffect is equivalent to componentDidMount (also didUpdate and willUnmount) so it only gets called after the first render, that's exactly what's happening:
render from HOC render form WrappedComponent ComponentDidMount from HOC useEffect from WrappedComponent
code :
RENDER GLOBAL
GLOBAL COMPONENTDIDMOUNT
USE EFFECT
Lifecycle issue using React Hooks

Lifecycle issue using React Hooks


By : user3353033
Date : March 29 2020, 07:55 AM
this will help first of all, you are calling async functions which will not be executed on the same order on the useEffect, so I propose you clean the functions a bit like:
code :
const checkIfUserIsEnabled = (user) => {
  if (user)
    setUser({ enabled: true, ...user })
}
const getUser = () => {
  let URL = `http://localhost:8080/users/finduserbytoken?id=`;
  const res = await fetch(URL);
  const user = res.json()
  checkIfUserIsEnabled(user)
}


useEffect(() => {
  verifyEmail(getTokenIdFromURL)
    .then(verified => {
      getUser()
    })
}, []);


  return (
        <div className="emailVerificationWrapper">
           <h1>{` Result is ${user.enabled}`}</h1>
           <br/>
           <div>Current User State:</div>
           <pre>{JSON.stringify(usre)}</pre>
        </div>
    )

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