feat(Exists): Add exits method

To check the existence of a DataPath.

See #19

src/JsonDB.ts

@@ -134,6 +134,22 @@ export default class JsonDB {
         return this.retrieveData(path, false)
     }
 
+    /**
+     * Check for existing datapath
+     * @param dataPath
+     */
+    public exists(dataPath: string): boolean {
+        try {
+            this.getData(dataPath)
+            return true
+        } catch (e) {
+            if (e instanceof DataError) {
+                return false
+            }
+            throw e
+        }
+    }
+
     /**
      * Pushing data into the database
      * @param dataPath path leading to the data

test/02-jsondb.test.ts

@@ -89,6 +89,13 @@ describe('JsonDB', () => {
             db.push("/", object)
             expect(db.getData("/")).toBe(object)
         })
+
+        test('should have data at root', () => {
+            expect(db.exists('/test/test')).toBeTruthy()
+        })
+        test('should not have data at not related path', () => {
+            expect(db.exists('/test/test/nope')).toBeFalsy()
+        })
         test('should override the data at the root', () => {
             const object = {test: "test"}
             db.push("/", object)