聽說讀寫

 1 var firstName = "Mark";
 2 (function DisplayFirstName() {
 3     console.log(firstName);
 4 })();//必然輸出 Mark
 5 
 6 var lastName = "Aut";
 7 (function DisplayLastName() {
 8     var lastName = "Bru";
 9     console.log(lastName);
10 })();//必然輸出 Bru,  本地作用域的優先級高于全局作用域
11 
12 //那么下面這段代碼呢?
13 
14 var lastName = "Aut";
15 (function DisplayLastName() {
16     console.log(lastName);
17     var lastName = "Bru";
18     console.log(lastName);
19 })();//誰能猜出結果是什么?