@primer/react/lib/hooks/useSyncedState.js

An implementation of GitHub's Primer Design System using React

'use strict';

var React = require('react');

/**
 * When the value that initialized the state changes
 * this hook will update the state to the new value, immediately.
 *
 * This uses an Object.is comparison to determine if the value has changed by default
 *
 * If you use a non-primitive value as the initial value, you should provide a custom isEqual function
 *
 * This is adapted almost directly from https://beta.reactjs.org/learn/you-might-not-need-an-effect#adjusting-some-state-when-a-prop-changes
 */

const useSyncedState = (initialValue, {
  isPropUpdateDisabled = false,
  isEqual = Object.is
} = {}) => {
  const [state, setState] = React.useState(initialValue);
  const [previous, setPrevious] = React.useState(initialValue);
  const nextInitialValue = initialValue instanceof Function ? initialValue() : initialValue;
  if (!isPropUpdateDisabled && !isEqual(previous, nextInitialValue)) {
    setPrevious(nextInitialValue);
    setState(nextInitialValue);
  }
  return [state, setState];
};

exports.useSyncedState = useSyncedState;