Randomly selects food option when clicked

HTML

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>
  
<h2 id="result">今天中午吃什麼？</h2>
<button onclick="pickFood()">抽籤！</button>

<script>
function pickFood() {
  let rand = Math.floor(Math.random() * 4); // 0~3
  switch(rand) {
    case 0:
      document.getElementById("result").innerText = "便當";
      break;
    case 1:
      document.getElementById("result").innerText = "炒飯";
      break;
    case 2:
      document.getElementById("result").innerText = "牛肉麵";
      break;
    case 3:
      document.getElementById("result").innerText = "壽司";
      break;
  }
}
</script>
  
</body>
</html>