lovecoding
/
W260426


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 判断是否为数字
        var str = "a" * 1
        console.log(str);
        console.log(isNaN(str));

        // 判断是否为数字
        var str = "3"
        if(str >= "0" && str <= "9"){
            console.log("是数字");
        }
    </script>
</body>
</html>