useRef Hook — JS: React Hooks

useRef() is usually used to access DOM elements for use 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 immediately after the component is mounted, but before the hooks are called. To do this, don't forget to set the ref attribute for the desired element.

Another way to use useRef() is to store any 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 the component is called. In terms of 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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