diff --git a/src/arrayMethodJoin.js b/src/arrayMethodJoin.js
index 3a62201c..0e90ae95 100644
--- a/src/arrayMethodJoin.js
+++ b/src/arrayMethodJoin.js
@@ -4,8 +4,26 @@
  * Implement method join
  */
 function applyCustomJoin() {
-  [].__proto__.join2 = function(separator) {
-    // write code here
+  [].__proto__.join2 = function(separator = ',') {
+    let resultString = '';
+
+    for (let i = 0; i < this.length - 1; i++) {
+      const element = this[i];
+
+      if (element !== undefined && element !== null) {
+        resultString += element;
+      }
+
+      resultString += separator;
+    }
+
+    const lastElement = this[this.length - 1];
+
+    if (lastElement === undefined || lastElement === null) {
+      return resultString;
+    }
+
+    return resultString + this[this.length - 1];
   };
 }