objShallowEqual.js

objShallowEqual.js

// OWNERS: dounan
// @flow

/**
 * Shallow equality comparison of the object values
 * @param  {Object} objA - Source object
 * @param  {Object} objB - Object to compare to
 * @param  {Function} customizer - Custom equality comparison. Return undefined
 *     to use the default comparator.
 * @return {Boolean} true iff objA and objB are shallowly equal
 */
export default function(objA: ?{}, objB: ?{}, customizer?: Customizer): boolean {
  if (objA === objB) {
    return true;
  }
  if (!objA || !objB) {
    return false;
  }
  const keysA = Object.keys(objA);
  const keysB = Object.keys(objB);
  if (keysA.length !== keysB.length) {
    return false;
  }
  const inObjB = Object.prototype.hasOwnProperty.bind(objB);
  for (let i = 0, n = keysA.length; i < n; i++) {
    const k = keysA[i];
    if (!inObjB(k)) {
      const a = objA[k];
      const b = objB[k];
      let result;
      if (customizer) {
        result = customizer(a, b, k);
      }
      result = result === undefined ? a === b : result;
      if (!result) {
        return false;
      }
    }
  }
  return true;
}

export type Customizer = (a: mixed, b: mixed, key: string) => boolean;