W3Schools 试用编辑器 - W3Schools 中文教程

获取您自身网站

<!DOCTYPE html>
<html>
<body>
<h1>JavaScript Operators</h1>
<h2>The typeof Operator</h2>

<p>The typeof operator returns the type of a variable, object, function or expression:</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML = 
"'John' is " + typeof "John" + "<br><br>" +
"('John' + 'Doe') is " + typeof ("John" + "Doe") + "<br><br>" +
"3.14 is " + typeof 3.14 + "<br><br>" +
"(33 + 66) is " + typeof (33 + 66) + "<br><br>" +
"NaN is " + typeof NaN + "<br><br>" +
"1234n is " + typeof 1234n + "<br><br>" +
"true is " + typeof true + "<br><br>" +
"false is " + typeof false + "<br><br>" +
"[1, 2, 3, 4] is " + typeof [1, 2, 3, 4] + "<br><br>" +
"{name:'John', age:34} is " + typeof {name:'John', age:34} + "<br><br>" +
"new Date() is " + typeof new Date() + "<br><br>" +
"new Set() is " + typeof new Set() + "<br><br>" +
"new Map() is " + typeof new Map() + "<br><br>" +
"Symbol() is " + typeof Symbol() + "<br><br>" +
"function () {} is " + typeof function () {} + "<br><br>" +
"x is " + typeof x + "<br><br>" +
"null is " + typeof null;
</script>

</body>
</html>