What is isNaN in javascript

javascript's isNaN is a built-in function used to check whether its parameter is a non-numeric value. Its usage syntax is "isNaN(value)", and the parameter value specifies the value to be detected.

The operating environment of this article: Windows 7 system, javascript version 1.8.5, Dell G3 computer.

What is isNaN of javascript?

isNaN() function is used to check whether its argument is a non-numeric value.

If the parameter value is NaN or a non-numeric value such as a string, object, or undefined, it will return true, otherwise it will return false.

Syntax

isNaN(value)

Parameters

value required. The value to detect.

All major browsers support isNaN() function

Example

Check whether the number is illegal:

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>");

The output result of the above example:

false
false
false
false
true
true

Recommended learning: "js Basic Tutorial"

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