feat(iskey): adding new util to match property names and paths

src/getTag.ts

@@ -1,5 +1,6 @@
 /**
  * Gets the `toStringTag` of `value`.
+ *
  * @private
  * @param {*} value The value to query.
  * @returns {string} Returns the `toStringTag`.

src/isKey.test.ts

@@ -0,0 +1,35 @@
+import { isKey } from './isKey';
+
+describe('isKey', () => {
+  describe('when only passing the value argument', () => {
+    it('should get true', () => {
+      expect(isKey(1)).toEqual(true);
+      expect(isKey(Symbol())).toEqual(true);
+      expect(isKey('attribute')).toEqual(true);
+      expect(isKey('spaced attribute')).toEqual(true);
+      expect(isKey(true)).toEqual(true);
+      expect(isKey(null)).toEqual(true);
+      expect(isKey(undefined)).toEqual(true);
+    });
+    it('should get false', () => {
+      expect(isKey([1, ''])).toEqual(false);
+      expect(isKey('something[test]')).toEqual(false);
+      expect(isKey('a.b')).toEqual(false);
+    });
+  });
+  describe('when passing the value and an object', () => {
+    const obj = {
+      '[a]': 5,
+      'b.c': true
+    };
+
+    it('should get true', () => {
+      expect(isKey('[a]', obj)).toEqual(true);
+      expect(isKey('b.c', obj)).toEqual(true);
+    });
+    it('should get false', () => {
+      expect(isKey('[b]', obj)).toEqual(false);
+      expect(isKey('c.d', obj)).toEqual(false);
+    });
+  });
+});

src/isKey.ts

@@ -0,0 +1,55 @@
+import { isSymbol } from './isSymbol';
+
+/** Used to match property names within property paths. */
+const reIsDeepProp = /\.|\[(?:[^[\]]*|(["'])(?:(?!\1)[^\\]|\\.)*?\1)\]/;
+const reIsPlainProp = /^\w*$/; //maches any word caracter (alphanumeric and underscore)
+
+/**
+ * Checks if `value` is a property name and not a property path.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @param {Object} [object] The object to query keys on.
+ * @returns {boolean} Returns `true` if `value` is a property name, else `false`.
+ * @example
+ * ```javascript
+ * isKey(1)
+ * // => true
+ *
+ * isKey('example[test]')
+ * // => false
+ *
+ * isKey('a.b')
+ * // => false
+ *
+ * const obj = {
+ *   '[a]': 5,
+ *   'b.c': true
+ * };
+ *
+ * isKey('[a]', obj)
+ * // => true
+ *
+ * isKey('b.c', obj)
+ * // => true
+ * ```
+ */
+export function isKey(value: any, object?: object): boolean {
+  if (Array.isArray(value)) {
+    return false;
+  }
+  const type = typeof value;
+  if (
+    type === 'number' ||
+    type === 'boolean' ||
+    value === null ||
+    isSymbol(value)
+  ) {
+    return true;
+  }
+  return (
+    reIsPlainProp.test(value) ||
+    !reIsDeepProp.test(value) ||
+    (object !== null && value in Object(object))
+  );
+}

src/memoizeCapped.ts

@@ -7,6 +7,7 @@ export const MAX_MEMOIZE_SIZE = 500;
 /**
  * A specialized version of `memoize` which clears the memoized function's
  * cache when it exceeds `MAX_MEMOIZE_SIZE`.
+ *
  * @private
  * @param {Function} func The function to have its output memoized.
  * @returns {Function} Returns the new memoized function.