shallowEqual

shallowEqual.ts

// source code: https://github.com/facebook/react/blob/master/packages/shared/shallowEqual.js
// TS Playgound: https://tsplay.dev/Nr272N

const shallowEqual = (objA: any, objB: any): boolean => {
  if (Object.is(objA, objB)) {
    return true;
  }

  if (
    typeof objA !== 'object' ||
    objA === null ||
    typeof objB !== 'object' ||
    objB === null
  ) {
    return false;
  }

  const keysA = Object.keys(objA);
  const keysB = Object.keys(objB);

  if (keysA.length !== keysB.length) {
    return false;
  }

  for (let i = 0; i < keysA.length; i++) {
    if (
      !objB.hasOwnProperty(keysA[i]) || // objB 中沒有該屬性
      !Object.is(objA[keysA[i]], objB[keysA[i]]) //  objA 和 objB 中該屬性的值不同
    ) {
      return false;
    }
  }

  return true;
};

console.log(shallowEqual({ foo: 'foo' }, { foo: 'foo' }));