Javascript basic tutorial typeof operator

typeof operator

typeof is used to detect the data type of variables. The following characters will be returned for values and variables

数据类型2.png

Undefined

In JavaScript, undefined is a variable that has no set value.

typeof A variable with no value will return undefined.

Let’s write an example below:

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>检测数据类型</title>
	<script type="text/javascript">
		var box;
		document.write(typeof box);
	</script>
</head>
<body>

</body>
</html>

The above code will output undiffed

Boolean type

The following example:

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>检测数据类型</title>
	<script type="text/javascript">
		var box= true;
		document.write(typeof box);
	</script>
</head>
<body>

</body>
</html>

string type

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>检测数据类型</title>
	<script type="text/javascript">
		var box="php 中文网";
		document.write(typeof box);
	</script>
</head>
<body>

</body>
</html>

number type

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>检测数据类型</title>
	<script type="text/javascript">
		var box=888;
		document.write(typeof box);
	</script>
</head>
<body>

</body>
</html>

Object

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>检测数据类型</title>
	<script type="text/javascript">
		var box={};
		document.write(typeof box);
	</script>
</head>
<body>

</body>
</html>

Note: An empty object means that the object has been created, but there is no content in it

NULL empty

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>检测数据类型</title>
	<script type="text/javascript">
		var box=null;
		document.write(typeof box);
	</script>
</head>
<body>

</body>
</html>

function function

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>检测数据类型</title>
	<script type="text/javascript">
		function box(){

		}
		document.write(typeof box);
	</script>
</head>
<body>

</body>
</html>

Note: box is a function function. The return value is function box(){}. The returned character channeling type is function

Continuing Learning

new file

<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>检测数据类型</title> <script type="text/javascript"> var box; document.write(typeof box); </script> </head> <body> </body> </html>

submit Reset Code

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Javascript basic tutorial typeof operator

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