[React 18] useId

A new hook for version 18 of React is useId. Frequently in React you need unique identifiers to associate two objects together. An example of this would be making sure a label and an input are associated together by the htmlFor attribute.

Previously you could maintain some sort of unique counter that was tracked across renders. With concurrent React and batching in version 18 that's no longer possible. useId will give you a consistent via a hook so that they can always be the same.

This is useful for the thing we see above: we have a label which needs a for attribute that corresponds to an input. We would either need to use some piece of data/parameter that we'd pass into the component that would serve as the key or we can use this hook to give it a unique ID.

If you need multiple IDs in the same component just do {id}-name, {id}-address, ``{id}-number, etc. No need to call useId` multiple times.

This is safe across server-side renders and client-side.

import { useId } from 'react';

function LabelInputPair() {
  const id = useId();
  return (
    <div style={{ marginBottom: '50px' }}>
      <label htmlFor={id}>
        Click on this label and it'll highlight the input {id}
      </label>
      <br />
      <input type="text" id={id} placeholder={`input id ${id}`} />
    </div>
  );
}

export default function UseIdComponent() {
  return (
    <>
      <LabelInputPair />
      <LabelInputPair />
      <LabelInputPair />
      <LabelInputPair />
    </>
  );
}