NaN refers to Not a Number , which is used for identifying wether a variable is having a number or not ?

Check whether a number is an illegal number or not... Example: 1) var A1 = isNaN(523) .....output:false 2) var B1 = isNaN("12").....output :true

Not a number ,which used in client side to check input is number or not

NaN is Not a Number , which is used for identifying that a variable is a number or not ? This function returns true if the value is NaN, and false if not.

most of the time NaN is used whether the given value is number or not

that is 'Not a Number' it is use to check the given value is number or not

It simply means the input you enter NaN(Not a Number)

The isNaN() function determines whether a value is an illegal number (Not-a-Number). This function returns true if the value is NaN, and false if not. E.g.:- var a = isNaN(123) Out:-false and var e = isNaN("Hello") Out:- true