Develop

src/arrayMethodJoin.js

@@ -4,9 +4,23 @@
  * Implement method join
  */
 function applyCustomJoin() {
-  [].__proto__.join2 = function(separator) {
-    // write code here
+  [].__proto__.join2 = function(separator = ',') {
+    let joinedString = '';
+
+    for (let i = 0; i < this.length; i++) {
+      if (this[i] !== null && this[i] !== undefined) {
+        joinedString += this[i];
+      }
+
+      if (i < this.length - 1) {
+        joinedString += separator;
+      }
+    }
+
+    return joinedString;
   };
 }
 
+applyCustomJoin([0, 1, 2, 3]);
+
 module.exports = applyCustomJoin;