Unlock the Power of Finite Numbers

The Syntax

The isFinite() function takes a single parameter, testValue, which is the value to be tested for finiteness. The syntax is straightforward:

isFinite(testValue)

Return Values

The isFinite() function returns:

• false if the argument is Infinity, NaN (Not a Number), or undefined
• true for all other arguments

Real-World Examples

Let’s put isFinite() to the test!

In our first example, we’ll check if the value 5463 is finite:

console.log(isFinite(5463)); // true

As expected, the output is true, since 5463 is a finite number.

In our second example, we’ll see that isFinite() returns false for Infinity and undefined:

console.log(isFinite(Infinity)); // false
console.log(isFinite(undefined)); // false

In our third example, we’ll see that isFinite() returns false for NaN (Not a Number) and null:

console.log(isFinite(NaN)); // false
console.log(isFinite(null)); // false

A Key Benefit

One of the most significant advantages of isFinite() is that it’s a top-level function, meaning it’s not associated with any object or class. This means you can call it from anywhere without creating an instance, making it a convenient and powerful tool in your JavaScript toolkit.

Related Topic: isNaN()

If you’re interested in learning more about working with numbers in JavaScript, be sure to check out the isNaN() function, which checks if a value is Not a Number (NaN).