Refactor peek function in Stack.

trekhleb · trekhleb · commit 114748b876a2 · 2018-05-24T09:10:48.000+03:00
diff --git a/src/data-structures/stack/Stack.js b/src/data-structures/stack/Stack.js
@@ -16,7 +16,7 @@ export default class Stack {
    * @return {*}
    */
   peek() {
-    if (!this.linkedList.tail) {
+    if (this.isEmpty()) {
       return null;
     }
 
