[Fix] properly compare RegExp objects

 - [Tests] add tests with `Object.create`

index.js

@@ -1,6 +1,8 @@
 var objectKeys = require('object-keys');
 var isArguments = require('is-arguments');
 var is = require('object-is');
+var isRegex = require('is-regex');
+var flags = require('regexp.prototype.flags');
 
 function deepEqual(actual, expected, options) {
   var opts = options || {};
@@ -10,6 +12,15 @@ function deepEqual(actual, expected, options) {
     return true;
   }
 
+  var actualIsRegex = isRegex(actual);
+  var expectedIsRegex = isRegex(expected);
+  if (actualIsRegex || expectedIsRegex) {
+    if (actualIsRegex !== expectedIsRegex) {
+      return false;
+    }
+    return actual.source === expected.source && flags(actual) === flags(expected);
+  }
+
   if (actual instanceof Date && expected instanceof Date) {
     return actual.getTime() === expected.getTime();
   }

package.json

@@ -16,8 +16,10 @@
   },
   "dependencies": {
     "is-arguments": "^1.0.4",
+    "is-regex": "^1.0.4",
     "object-is": "^1.0.1",
-    "object-keys": "^1.1.1"
+    "object-keys": "^1.1.1",
+    "regexp.prototype.flags": "^1.2.0"
   },
   "devDependencies": {
     "@ljharb/eslint-config": "^13.1.1",

test/cmp.js

@@ -228,3 +228,46 @@ test('zeroes', function (t) {
 
   t.end();
 });
+
+test('test objects', { skip: !Object.create }, function (t) {
+  var a = { a: 'A' };
+  var b = Object.create(a);
+  b.b = 'B';
+  var c = Object.create(a);
+  c.b = 'C';
+
+  t.notOk(equal(b, c), 'two objects with the same [[Prototype]] but a different own property are not equal');
+  t.notOk(equal(c, b), 'two objects with the same [[Prototype]] but a different own property are not equal');
+
+  t.notOk(equal(b, c, { strict: true }), 'strict: two objects with the same [[Prototype]] but a different own property are not equal');
+  t.notOk(equal(c, b, { strict: true }), 'strict: two objects with the same [[Prototype]] but a different own property are not equal');
+
+  t.end();
+});
+
+test('regexes vs dates', function (t) {
+  var d = new Date(1387585278000);
+  var r = /abc/;
+
+  t.notOk(equal(d, r), 'date and regex are not equal');
+  t.notOk(equal(r, d), 'regex and date are not equal');
+
+  t.notOk(equal(d, r, { strict: true }), 'strict: date and regex are not equal');
+  t.notOk(equal(r, d, { strict: true }), 'strict: regex and date are not equal');
+
+  t.end();
+});
+
+test('regexen', function (t) {
+  t.notOk(equal(/abc/, /xyz/), 'two different regexes are not equal');
+  t.notOk(equal(/xyz/, /abc/), 'two different regexes are not equal');
+  t.ok(equal(/abc/, /abc/), 'two same regexes are equal');
+  t.ok(equal(/xyz/, /xyz/), 'two same regexes are equal');
+
+  t.notOk(equal(/abc/, /xyz/, { strict: true }), 'strict: two different regexes are not equal');
+  t.notOk(equal(/xyz/, /abc/, { strict: true }), 'strict: two different regexes are not equal');
+  t.ok(equal(/abc/, /abc/, { strict: true }), 'strict: two same regexes are not equal');
+  t.ok(equal(/xyz/, /xyz/, { strict: true }), 'strict: two same regexes are not equal');
+
+  t.end();
+});