使用该toString()方法将Number转换为字符串，然后该length()方法将为您提供长度。
您可以尝试运行以下代码以了解如何获取数字的长度-
<!DOCTYPE html>
<html>
<body>
<script>
var num1 = 344;
var num2 = 149856;
document.write("Length of number "+num1+" = "+ num1.toString().length);
document.write("<br>Length of number "+num2+" = "+ num2.toString().length);
</script>
</body>
</html>输出结果
Length of number 344 = 3 Length of number 149856 = 6