Add "isWeakRef" function

.eslintrc

@@ -6,7 +6,8 @@
     "browser": true,
     "es6": true,
     "jest": true,
-    "node": true
+    "node": true,
+    "es2021": true
   },
   "globals": {
     "BigInt": "readonly",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "lodash",
-  "version": "5.0.0",
+  "version": "5.0.1",
   "license": "MIT",
   "private": true,
   "main": "dist/lodash.js",

src/isWeakRef.ts

@@ -0,0 +1,23 @@
+import getTag from './.internal/getTag.js';
+import isObjectLike from './isObjectLike.js';
+
+/**
+ * Checks if `value` is classified as a `WeakRef` object.
+ *
+ * @since 5.0.1
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is a weak ref, else `false`.
+ * @example
+ *
+ * isWeakRef(new WeakRef)
+ * // => true
+ *
+ * isWeakRef(new WeakMap)
+ * // => false
+ */
+function isWeakRef(value) {
+    return isObjectLike(value) && getTag(value) === '[object WeakRef]';
+}
+
+export default isWeakRef;

test/isType-checks.spec.js

@@ -56,6 +56,7 @@ describe('isType checks', () => {
             'isUndefined',
             'isWeakMap',
             'isWeakSet',
+            'isWeakRef',
         ];
 
         lodashStable.each(funcs, (methodName) => {

test/isWeakRef.spec.js

@@ -0,0 +1,43 @@
+import lodashStable from 'lodash';
+import { weakRef, falsey, stubFalse, args, slice, set, map, weakSet, weakMap, symbol, realm } from './utils';
+import isWeakRef from '../src/isWeakRef';
+
+describe('isWeakRef', () => {
+    it('should return `true` for weak refs', () => {
+        if (WeakRef) {
+            expect(isWeakRef(weakRef)).toBe(true);
+        }
+    });
+
+    it('should return `false` for non weak refs', () => {
+        const expected = lodashStable.map(falsey, stubFalse);
+
+        const actual = lodashStable.map(falsey, (value, index) =>
+            index ? isWeakRef(value) : isWeakRef(),
+        );
+
+        expect(actual).toEqual(expected);
+
+        expect(isWeakRef(args)).toBe(false);
+        expect(isWeakRef([1, 2, 3])).toBe(false);
+        expect(isWeakRef(true)).toBe(false);
+        expect(isWeakRef(new Date())).toBe(false);
+        expect(isWeakRef(new Error())).toBe(false);
+        expect(isWeakRef(slice)).toBe(false);
+        expect(isWeakRef({ a: 1 })).toBe(false);
+        expect(isWeakRef(1)).toBe(false);
+        expect(isWeakRef(/x/)).toBe(false);
+        expect(isWeakRef('a')).toBe(false);
+        expect(isWeakRef(set)).toBe(false);
+        expect(isWeakRef(map)).toBe(false);
+        expect(isWeakRef(weakSet)).toBe(false);
+        expect(isWeakRef(weakMap)).toBe(false);
+        expect(isWeakRef(symbol)).toBe(false);
+    });
+
+    it('should work with weak refs from another realm', () => {
+        if (realm.weakRef) {
+            expect(isWeakRef(realm.weakRef)).toBe(true);
+        }
+    });
+});

test/utils.js

@@ -74,6 +74,7 @@ const Symbol = root.Symbol;
 const Uint8Array = root.Uint8Array;
 const WeakMap = root.WeakMap;
 const WeakSet = root.WeakSet;
+const WeakRef = root.WeakRef;
 
 const arrayBuffer = ArrayBuffer ? new ArrayBuffer(2) : undefined;
 const map = Map ? new Map() : undefined;
@@ -82,6 +83,7 @@ const set = Set ? new Set() : undefined;
 const symbol = Symbol ? Symbol('a') : undefined;
 const weakMap = WeakMap ? new WeakMap() : undefined;
 const weakSet = WeakSet ? new WeakSet() : undefined;
+const weakRef = WeakRef ? new WeakRef() : undefined;
 
 /** Math helpers. */
 const add = function (x, y) {
@@ -1152,6 +1154,7 @@ lodashStable.attempt(() => {
                 "    'undefined': undefined,",
                 "    'weakMap': root.WeakMap ? new root.WeakMap : undefined,",
                 "    'weakSet': root.WeakSet ? new root.WeakSet : undefined",
+                "    'weakRef': root.WeakRef ? new root.WeakRef : undefined",
                 '  };',
                 '',
                 `  ['${arrayViews.join("', '")}'].forEach(function(type) {`,
@@ -1208,6 +1211,7 @@ lodashStable.attempt(() => {
             "  'undefined': undefined,",
             "  'weakMap': root.WeakMap ? new root.WeakMap : undefined,",
             "  'weakSet': root.WeakSet ? new root.WeakSet : undefined",
+            "  'weakRef': root.WeakRef ? new root.WeakRef : undefined",
             '};',
             '',
             `_.each(['${arrayViews.join("', '")}'], function(type) {`,
@@ -1301,6 +1305,7 @@ export {
     symbol,
     weakMap,
     weakSet,
+    weakRef,
     add,
     doubled,
     isEven,