JavaScript isNaN () function
JavaScript Global Functions Definition and Usage
isNaN () function is used to check whether the parameters are non-numeric.
If this parameter is non-numeric or string value NaN, the object, undefined and other returns true, otherwise it returns false.
grammar
isNaN(value)
| 参数 | 描述 |
|---|---|
| value | 必需。要检测的值。 |
Browser Support
All major browsers support isNaN () function
Examples
Examples
Check whether a number is illegal:
<script>
document.write(isNaN(123)+ "<br>");
document.write(isNaN(-1.23)+ "<br>");
document.write(isNaN(5-2)+ "<br>");
document.write(isNaN(0)+ "<br>");
document.write(isNaN("Hello")+ "<br>");
document.write(isNaN("2005/12/12")+ "<br>");
</script>
document.write(isNaN(123)+ "<br>");
document.write(isNaN(-1.23)+ "<br>");
document.write(isNaN(5-2)+ "<br>");
document.write(isNaN(0)+ "<br>");
document.write(isNaN("Hello")+ "<br>");
document.write(isNaN("2005/12/12")+ "<br>");
</script>
Examples of the above output:
false
false
false
false
true
true
false
false
false
true
true
try it"
JavaScript Global Functions