react-sweet-state/lib/esm/utils/shallow-equal.js

Global + local state combining the best of Redux and Context API

// Mostly copied from fbjs/packages/fbjs/src/core/shallowEqual.js
// enhanced with keys cache as might get called multiple times with same args
const hasOwnProperty = Object.prototype.hasOwnProperty;
const CACHE = new WeakMap();
export default function shallowEqual(objA, objB) {
  if (objA === objB) {
    return true;
  }

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

  if (Array.isArray(objA) && Array.isArray(objB)) {
    // do array comparison
    if (objA.length !== objB.length) {
      return false;
    }

    for (let i = 0; i < objA.length; i++) {
      if (objA[i] !== objB[i]) {
        return false;
      }
    }

    return true;
  } else {
    // Handle Date, RegExp, String, Number, ... and complex objects
    const strA = '' + objA;
    const strB = '' + objB;

    if (strA !== strB || strA[0] === '[' && strA !== '[object Object]') {
      return false;
    } // do object comparison


    let keysA;

    if (CACHE.has(objA)) {
      keysA = CACHE.get(objA);
    } else {
      keysA = Object.keys(objA);
      CACHE.set(objA, keysA);
    }

    let keysB;

    if (CACHE.has(objB)) {
      keysB = CACHE.get(objB);
    } else {
      keysB = Object.keys(objB);
      CACHE.set(objB, keysB);
    }

    if (keysA.length !== keysB.length) {
      return false;
    } // Test for A's keys different from B.


    for (let i = 0; i < keysA.length; i++) {
      if (!hasOwnProperty.call(objB, keysA[i]) || objA[keysA[i]] !== objB[keysA[i]]) {
        return false;
      }
    }

    return true;
  }
}