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How useEffect dependency work in React?

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M Hassan khan answered on July 6, 2022 Popularity 9/10 Helpfulness 1/10

answer How useEffect dependency work in React?

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How useEffect dependency work in React?

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the [] at the end of the useEffect is where you declare your 
data dependencies.
React wants to know when to run that effect again.

If You don't give it any data dependencies, it assumes any time 
any hook changes that you should run the effect again. 

You can instead provide which hooks to watch for changes for. 
If we actually only want it to run once, on creation of the component, 
and then to not run that effect again. 

You can accomplish this only-run-on-creation by providing 
an empty array [].

Popularity 9/10 Helpfulness 1/10 Language javascript

Source: Grepper

Tags: javascript use-effect

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Contributed on Nov 23 2022

M Hassan khan

0 Answers Avg Quality 2/10

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const usePrevious = (value, initialValue) => {
  const ref = useRef(initialValue);
  useEffect(() => {
    ref.current = value;
  });
  return ref.current;
};

Popularity 8/10 Helpfulness 3/10 Language javascript

Source: stackoverflow.com

Tags: javascript j

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Contributed on Mar 02 2023

Graceful Gorilla

0 Answers Avg Quality 2/10

useeffect dependency check

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const useEffectDebugger = (effectHook, dependencies, dependencyNames = []) => {
  const previousDeps = usePrevious(dependencies, []);

  const changedDeps = dependencies.reduce((accum, dependency, index) => {
    if (dependency !== previousDeps[index]) {
      const keyName = dependencyNames[index] || index;
      return {
        ...accum,
        [keyName]: {
          before: previousDeps[index],
          after: dependency
        }
      };
    }

    return accum;
  }, {});

  if (Object.keys(changedDeps).length) {
    console.log('[use-effect-debugger] ', changedDeps);
  }

  useEffect(effectHook, dependencies);
};

Popularity 7/10 Helpfulness 2/10 Language javascript

Source: stackoverflow.com

Tags: javascript use-effect u

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Contributed on Mar 02 2023

Graceful Gorilla

0 Answers Avg Quality 2/10

useEffect react dependency

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function EffectsDemoTwoStatesWithDependeny() {
  const [title, setTitle] = useState("default title");
  const titleRef = useRef();
  const [darkMode, setDarkMode] = useState(false);
  useEffect(() => {
    console.log("useEffect");
    document.title = title;
  }, [title]);
  console.log("render");
  const handleClick = () => setTitle(titleRef.current.value);
  const handleCheckboxChange = () => setDarkMode((prev) => !prev);
  return (
    <div className={darkMode ? "view dark-mode" : "view"}>
      <label htmlFor="darkMode">dark mode</label>
      <input
        name="darkMode"
        type="checkbox"
        checked={darkMode}
        onChange={handleCheckboxChange}
      />
      <input ref={titleRef} />
      <button onClick={handleClick}>change title</button>
    </div>
  );
}

Popularity 10/10 Helpfulness 2/10 Language javascript

Source: blog.logrocket.com

Tags: javascript j

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Contributed on Jul 06 2022

Depressed Dugong

0 Answers Avg Quality 2/10

How useEffect dependency work in React?

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