index.html
<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>My JavaScript</title>
</head>
<body>
<script src="main.js"></script>
</body>
</html>main.js
'use strict';
{
let start = 'Tokyo';
let goal = 'Osaka';
//start = goal;
//goal = start;
//let temp = "";
//temp = start;
//start = goal;
//goal = temp;
[goal, start] = [start, goal]
console.log(start);
console.log(goal);
}