diff --git a/src/arrayMethodJoin.js b/src/arrayMethodJoin.js
index 3a62201c..568d471c 100644
--- a/src/arrayMethodJoin.js
+++ b/src/arrayMethodJoin.js
@@ -4,8 +4,19 @@
  * Implement method join
  */
 function applyCustomJoin() {
-  [].__proto__.join2 = function(separator) {
+  [].__proto__.join2 = function(separator = ',') {
     // write code here
+    let resultString = '';
+
+    for (let i = 0; i < this.length; i++) {
+      if (typeof (this[i]) !== 'undefined' && this[i] !== null) {
+        resultString += `${this[i]}`;
+      }
+
+      resultString += `${i < this.length - 1 ? separator : ''}`;
+    }
+
+    return resultString;
   };
 }