useRef Hook — JS: React Hooks

Usually we work with the useRef() hook to use DOM elements in useEffect() or event handlers:

const Input = () => {
  // null – initial value
  const inputEl = useRef(null);

  const onButtonClick = () => {
    // `current` points to the mounted `input` element `input`
    inputEl.current.focus();
  };

  return (
    <>
      <input ref={inputEl} type="text" />
      <button onClick={onButtonClick}>Focus</button>
    </>
  );
}

The value inside inputEl appears after we mount the component but before we call the hooks. Don't forget to set the ref attribute for the desired element when you do so.

Another way to use useRef() is to store data between component calls. This hook returns a regular object with the current property inside.

The only difference between this object and the manually created { current: ... } is that the hook returns the same object every time we call the component. In its behavior, useRef() is similar to using a regular property inside a class component (this.someproperty).

Below is an example of how you can save the previous state using useRef():

See the Pen use_ref by Hexlet (@hexlet) on CodePen.

Recommended materials

1. Using the useRef Hook
2. Measure a Dom node

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