Js determines whether the variable is a number

Js determines whether the variable is a number. Here we mainly introduce the use of the isNaN function in js. The following describes the specific examples.

document.write(isNaN(123));//falsedocument.write(isNaN(-1.23));//falsedocument.write(isNaN(5-2));//falsedocument.write(isNaN(0));//falsedocument.write(isNaN("Hello"));//truedocument.write(isNaN("2005/12/12"));//truedocument.write(isNaN("6/2"));//truedocument.write(isNaN("3"));//false

The following describes the isNaN Function Definition, usage, and syntax.

Definition and usage

The isNaN () function is used to check whether the parameter is a non-numeric value.

Syntax

IsNaN (x) x is required. The value to be detected.

Return Value

If x is a special non-numeric value NaN (or can be converted to such a value), the returned value is true. If x is another value, false is returned.

Description

The isNaN () function can be used to determine whether the parameter is NaN. This value indicates an invalid number (for example, the result obtained after being divided by 0 ).

If the result of comparing NaN with any value (including its own) is false, you cannot use the = OR = Operator to determine whether a value is NaN. Because of this, the isNaN () function is required.

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