Yogesh Chauhan's Blog

# The difference between isFinite() method and isFinite() function in JavaScript

in JavaScript on July 8, 2020

### JavaScript isFinite() Function

The isFinite() function determines whether a number is a finite, legal number.

If  needed, the parameter is first converted to a number.

This function returns false if the value is +infinity, -infinity, or NaN (Not-a-Number), otherwise it returns true.

#### Syntax

``````
isFinite(testValue)

where testValue = The value to be tested for finiteness.
``````

#### Examples

``````
console.log(isFinite(1)) //true
console.log(isFinite(-1.99)) //true
console.log(isFinite(4-2)) //true
console.log(isFinite(0)) //true
console.log(isFinite("1")) //true
console.log(isFinite("string")) //false
console.log(isFinite("2020/5/5")) //false``````

### JavaScript isFinite() Method

Checks whether a value is a finite number.

This method returns true if the value is of the type Number, and equates to a finite number. Otherwise it returns false.

#### Examples

``````
Number.isFinite(1) //true
Number.isFinite(-1.1) //true
Number.isFinite(4-2) //true
Number.isFinite(0) //true
Number.isFinite('1') //false
Number.isFinite('String') //false
Number.isFinite('2020/5/5') //false
Number.isFinite(Infinity) //false
Number.isFinite(-Infinity) //false
Number.isFinite(0 / 0) //false``````

You must have noticed the difference.

If not, let me show here separately.

``````
//function
console.log(isFinite("1")) //true

//method
Number.isFinite('1') //false

//in case you're thinking about quotes, they don't matter. You can use either one.
``````

Almost everything is the same about the method and function, except one thing.

The global isFinite() function converts the tested value to a Number, then tests it.

Number.isFinite() does not convert the values to a Number, and will not return true for any value that is not of the type Number.