useUpdateEffect

useUpdateEffect is a React hook that mimics the behavior of componentDidUpdate in function components.

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Install

• npm install use-update-effect --save or
• yarn add use-update-effect

Use

You use the useUpdateEffect the same way you would use the useEffect hook. Provide an effect callback and a dependency list, and the effect callback will only execute when the dependency list updates.

For a behavior exactly the same as componentDidUpdate, provide an empty ([]) or no (undefined) dependency list.

In the following example, there is no alert when the component mounts; but when the username changes, an alert appears.

import useUpdateEffect from 'use-update-effect';

function MyComponent({ username }) {
  useUpdateEffect(() => {
    alert(`Now logged in as ${username}!`);
  }, [username]);

  return <div>{username}</div>;
}

In the following example, a controlled input is allowed to have an in-flight value until "Apply" is clicked. By using an update effect, we override the in-flight value when a new controlled value is provided. This is useful when a controlled value may have more than one controlling component.

import useUpdateEffect from 'use-update-effect';

function MyComponent({ onChange, value }) {
  const [localValue, setLocalValue] = React.useState(value);

  useUpdateEffect(() => {
    setLocalValue(value);
  }, [value]);

  return (
    <>
      <input
        onChange={e => {
          setLocalValue(e.target.value);
        }}
        value={localValue}
      />
      <input onClick={onChange} type="submit" value="Apply" />
    </>
  );
}

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