解釋 JavaScript switch 語句中的嚴格比較?
JavaScript switch 語句僅使用嚴格比較 (===),並且不會轉換為型別,如果使用嚴格比較找不到匹配項,將立即執行 default 語句。
以下是 JavaScript switch 語句中嚴格比較的程式碼 −
示例
<!DOCTYPE html>
<html lang="en" >
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
body {
font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}
.result {
font-size: 20px;
font-weight: 500;
}
</style>
</head>
<body>
<h1>JavaScript Switch statement strict comparison</h1>
Enter day 1-7<input type="text" class="day" /><button class="Btn">
CHECK
</button>
<div style="color: green;" class="result"></div>
<h3>
Click on the above button to check if switch performs strict comparison or not
</h3>
<script>
let dayVal = document.querySelector(".day");
let resEle = document.querySelector(".result");
document.querySelector(".Btn").addEventListener("click", () => {
switch (dayVal.value) {
case 1:
resEle.innerHTML = "It's monday";
break;
case 2:
resEle.innerHTML = "It's tuesday";
break;
case 3:
resEle.innerHTML = "It's wednesday";
break;
case 4:
resEle.innerHTML = "It's thursday";
break;
case 5:
resEle.innerHTML = "It's friday";
break;
case 6:
resEle.innerHTML = "It's saturday";
break;
case 7:
resEle.innerHTML = "It's sunday";
break;
default:
resEle.innerHTML = "Enter a value between 1 - 7";
break;
}
});
</script>
</body>
</html>輸出
以上程式碼將產生以下輸出 −

輸入數字並單擊“檢查”時,由於 switch 總會執行嚴格比較,因此每次都會呼叫 default 語句 −

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