assert: improve deepEqual perf for large input

Use a Map instead of an array for checking previously found cyclic references. This reduces complexity for an array-of-objects case from O(n²) to O(n·log n). Fixes: #12842 PR-URL: #12849 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com> Reviewed-By: Refael Ackermann <refack@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

Author: addaleax

lib/assert.js

@@ -285,15 +285,24 @@ function _deepEqual(actual, expected, strict, memos) {
  // Note: this accounts for both named and indexed properties on Arrays.
 
  // Use memos to handle cycles.
- memos = memos || { actual: [], expected: [] };
- const actualIndex = memos.actual.indexOf(actual);
- if (actualIndex !== -1) {
- if (actualIndex === memos.expected.indexOf(expected)) {
+ if (!memos) {
+ memos = {
+ actual: { map: new Map(), position: 0 },
+ expected: { map: new Map(), position: 0 }
+ };
+ }
+
+ const actualPosition = memos.actual.map.get(actual);
+ if (actualPosition !== undefined) {
+ if (actualPosition === memos.expected.map.get(expected)) {
  return true;
  }
+ } else {
+ memos.actual.map.set(actual, memos.actual.position++);
+ }
+ if (!memos.expected.map.has(expected)) {
+ memos.expected.map.set(expected, memos.expected.position++);
  }
- memos.actual.push(actual);
- memos.expected.push(expected);
 
  return objEquiv(actual, expected, strict, memos);
 }