Function keyCheck

lib/internal/util/comparisons.js:470–521

(val1, val2, mode, memos, iterationType, keys2)

}

function keyCheck(val1, val2, mode, memos, iterationType, keys2) {
  // For all remaining Object pairs, including Array, objects and Maps,
  // equivalence is determined by having:
  // a) The same number of owned enumerable properties
  // b) The same set of keys/indexes (although not necessarily the same order)
  // c) Equivalent values for every corresponding key/index
  // d) For Sets and Maps, equal contents
  // Note: this accounts for both named and indexed properties on Arrays.
  const isArrayLikeObject = keys2 !== undefined;

  if (keys2 === undefined) {
    keys2 = ObjectKeys(val2);
  }
  let keys1;

  if (!isArrayLikeObject) {
    // The pair must have the same number of owned properties.
    if (mode === kPartial) {
      if (!partialSymbolEquiv(val1, val2, keys2)) {
        return false;
      }
    } else if (keys2.length !== (keys1 = ObjectKeys(val1)).length) {
      return false;
    } else if (mode === kStrict || mode === kStrictWithoutPrototypes) {
      for (const key of getOwnSymbols(val1)) {
        if (hasEnumerable(val1, key)) {
          ArrayPrototypePush(keys1, key);
        }
      }
      for (const key of getOwnSymbols(val2)) {
        if (hasEnumerable(val2, key)) {
          ArrayPrototypePush(keys2, key);
        }
      }
      if (keys1.length !== keys2.length) {
        return false;
      }
    }
  }

  if (keys2.length === 0 &&
      (iterationType === kNoIterator ||
        (iterationType === kIsArray && val2.length === 0) ||
        val2.size === 0)) {
    return true;
  }

  if (memos === null) {
    return objEquiv(val1, val2, mode, keys1, keys2, memos, iterationType);
  }
  return handleCycles(val1, val2, mode, keys1, keys2, memos, iterationType);
}

function handleCycles(val1, val2, mode, keys1, keys2, memos, iterationType) {
  // Use memos to handle cycles.