isNaN

Checks if a value when converted to a number is a special value NaN (not a number).

Note

isNaN differs from Number.isNaN in that isNaN converts the tested value to a number, while Number.isNaN does not. This may lead to unintuitive results, for example isNaN of string returns true because the string is converted to NaN which is a special value for not a number, however if the string is empty, Number.isNaN returns false because the empty string is converted to 0 which is a number.

In Math mode, bigfloat throws when converting it to a number, and thus isNaN will throw.

Syntax

function isNaN(value)

Parameters

• value

  Any numeric value.

Return value

Returns true if the value is NaN, false otherwise.

Examples

isNaN(NaN)

true

isNaN(1)

false

isNaN(Math.sqrt(-1))

true

isNaN("a string")

true

isNaN("")

false

Number.isNaN("a string")

false

See also

• Number.isNaN