3 files changed, 198 insertions, 1 deletions

diff --git a/.eslintrc.json b/.eslintrc.json
index 2f8306f7..3723d97d 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -110,6 +110,7 @@
                 "escapeRegExp": "readonly",
                 "deferPromise": "readonly",
                 "clone": "readonly",
+                "deepEqual": "readonly",
                 "generateId": "readonly",
                 "promiseAnimationFrame": "readonly",
                 "DynamicProperty": "readonly",
diff --git a/ext/mixed/js/core.js b/ext/mixed/js/core.js
index 81330893..72ab7474 100644
--- a/ext/mixed/js/core.js
+++ b/ext/mixed/js/core.js
@@ -176,6 +176,72 @@ const clone = (() => {
     return clone;
 })();
 
+const deepEqual = (() => {
+    // eslint-disable-next-line no-shadow
+    function deepEqual(value1, value2) {
+        if (value1 === value2) { return true; }
+
+        const type = typeof value1;
+        if (typeof value2 !== type) { return false; }
+
+        switch (type) {
+            case 'object':
+            case 'function':
+                return deepEqualInternal(value1, value2, new Set());
+            default:
+                return false;
+        }
+    }
+
+    function deepEqualInternal(value1, value2, visited1) {
+        if (value1 === value2) { return true; }
+
+        const type = typeof value1;
+        if (typeof value2 !== type) { return false; }
+
+        switch (type) {
+            case 'object':
+            case 'function':
+            {
+                if (value1 === null || value2 === null) { return false; }
+                const array = Array.isArray(value1);
+                if (array !== Array.isArray(value2)) { return false; }
+                if (visited1.has(value1)) { return false; }
+                visited1.add(value1);
+                return array ? areArraysEqual(value1, value2, visited1) : areObjectsEqual(value1, value2, visited1);
+            }
+            default:
+                return false;
+        }
+    }
+
+    function areObjectsEqual(value1, value2, visited1) {
+        const keys1 = Object.keys(value1);
+        const keys2 = Object.keys(value2);
+        if (keys1.length !== keys2.length) { return false; }
+
+        const keys1Set = new Set(keys1);
+        for (const key of keys2) {
+            if (!keys1Set.has(key) || !deepEqualInternal(value1[key], value2[key], visited1)) { return false; }
+        }
+
+        return true;
+    }
+
+    function areArraysEqual(value1, value2, visited1) {
+        const length = value1.length;
+        if (length !== value2.length) { return false; }
+
+        for (let i = 0; i < length; ++i) {
+            if (!deepEqualInternal(value1[i], value2[i], visited1)) { return false; }
+        }
+
+        return true;
+    }
+
+    return deepEqual;
+})();
+
 function generateId(length) {
     const array = new Uint8Array(length);
     crypto.getRandomValues(array);
diff --git a/test/test-core.js b/test/test-core.js
index 3e8b8414..2b29b7f1 100644
--- a/test/test-core.js
+++ b/test/test-core.js
@@ -32,7 +32,7 @@ const vm = new VM({
 vm.execute([
     'mixed/js/core.js'
 ]);
-const [DynamicProperty] = vm.get(['DynamicProperty']);
+const [DynamicProperty, deepEqual] = vm.get(['DynamicProperty', 'deepEqual']);
 
 
 function testDynamicProperty() {
@@ -161,9 +161,139 @@ function testDynamicProperty() {
     }
 }
 
+function testDeepEqual() {
+    const data = [
+        // Simple tests
+        {
+            value1: 0,
+            value2: 0,
+            expected: true
+        },
+        {
+            value1: null,
+            value2: null,
+            expected: true
+        },
+        {
+            value1: 'test',
+            value2: 'test',
+            expected: true
+        },
+        {
+            value1: true,
+            value2: true,
+            expected: true
+        },
+        {
+            value1: 0,
+            value2: 1,
+            expected: false
+        },
+        {
+            value1: null,
+            value2: false,
+            expected: false
+        },
+        {
+            value1: 'test1',
+            value2: 'test2',
+            expected: false
+        },
+        {
+            value1: true,
+            value2: false,
+            expected: false
+        },
+
+        // Simple object tests
+        {
+            value1: {},
+            value2: {},
+            expected: true
+        },
+        {
+            value1: {},
+            value2: [],
+            expected: false
+        },
+        {
+            value1: [],
+            value2: [],
+            expected: true
+        },
+        {
+            value1: {},
+            value2: null,
+            expected: false
+        },
+
+        // Complex object tests
+        {
+            value1: [1],
+            value2: [],
+            expected: false
+        },
+        {
+            value1: [1],
+            value2: [1],
+            expected: true
+        },
+        {
+            value1: [1],
+            value2: [2],
+            expected: false
+        },
+
+        {
+            value1: {},
+            value2: {test: 1},
+            expected: false
+        },
+        {
+            value1: {test: 1},
+            value2: {test: 1},
+            expected: true
+        },
+        {
+            value1: {test: 1},
+            value2: {test: {test2: false}},
+            expected: false
+        },
+        {
+            value1: {test: {test2: true}},
+            value2: {test: {test2: false}},
+            expected: false
+        },
+        {
+            value1: {test: {test2: [true]}},
+            value2: {test: {test2: [true]}},
+            expected: true
+        },
+
+        // Recursive
+        {
+            value1: (() => { const x = {}; x.x = x; return x; })(),
+            value2: (() => { const x = {}; x.x = x; return x; })(),
+            expected: false
+        }
+    ];
+
+    let index = 0;
+    for (const {value1, value2, expected} of data) {
+        const actual1 = deepEqual(value1, value2);
+        assert.strictEqual(actual1, expected, `Failed for test ${index}`);
+
+        const actual2 = deepEqual(value2, value1);
+        assert.strictEqual(actual2, expected, `Failed for test ${index}`);
+
+        ++index;
+    }
+}
+
 
 function main() {
     testDynamicProperty();
+    testDeepEqual();
 }