Added contains.js implementation

Author: Eugenie-A

Sprint-2/implement/contains.js

@@ -1,3 +1,12 @@
-function contains() {}
+function contains(object, propertyName) {
+  // return false if object is null/defined or not an object
+  if (object == null) return false;
+  // typeof check + reject arrays
+  if (typeof object !== "object") return false;
+  if (Array.isArray(object)) return false;
+
+  // Use hasOwnProperty to check only own properties
+  return Object.prototype.hasOwnProperty.call(object, propertyName);
+}
 
 module.exports = contains;