# The Weird World of Infinity in JavaScript

- 470

**The world of endlessness in JavaScript — explore the Infinity keyword .`Infinity`is a numeric value in JavaScript and corresponds to the mathematical representation of infinity. Technically, `Infinity` is classified as a property of the `window`object, similar to how variables in the global scope become properties of `window`**

## What is Infinity in JavaScript?

`Infinity`

is a numeric value in JavaScript and corresponds to the mathematical representation of infinity. Technically, `Infinity`

is classified as a property of the `window`

object, similar to how variables in the global scope become properties of `window`

*.* The value of `Infinity`

(positive infinity) is greater than any other number. Likewise, the value of `-Infinity`

(negative infinity) is smaller than any other number.

Despite being a numerical value, `Infinity`

cannot be iterated upon. For example, you would not be able to run it as a `for... of`

loop. You will be returned with an `Uncaught TypeError: Infinity is not iterable`

error.

```
// This won't work!
// Uncaught TypeError: Infinity is not iterable
for (let i of Infinity) {
console.log(i);
}
```

But you can use the `Infinity`

object as a ceiling or floor in your `for`

loops. Although this is not advisable as it will probably crash your PC.

```
// Don't do this!
for (let i=0; i<Infinity; i++){
// Infinite loop
}
// Don't do this!
for (let i=0; i>-Infinity; i--){
// Infinite loop
}
```

## When does Infinity occur?

If you console values and see for yourself, the console would display Infinity just as your number hits 309 digits regardless of the digit value(i.e: even 309 ones would be Infinity).

To be even more precise, according to the spec, `**Infinity**`

represents all values greater than `**1.7976931348623157e+308**`

**.**

Another instance where you will get Infinity as output is when you divide a number by zero.

```
console.log(90 / 0); // Infinity
console.log(-90 / 0); // -Infinity
```

This is different from what you see on a calculator as you would receive a “cannot divide by zero” or “undefined” type of error.

Another way of receiving `Infinity`

is by accessing them directly from the `Number`

object in JavaScript.

## How to check for Infinity?

You can use your own function like below. This method checks for both Positive and Negative `Infinity`

.

If you want to go for a builtin JS method, you can go with the `isFinite()`

method. The `isFinite()`

function determines whether a number is a finite, legal number. This function returns false if the value is +Infinity, -Infinity, or NaN (Not-a-Number), otherwise it returns true.

**NOTE
The**

`**isFinite()**`

**method returns true for**

`**null**`

**. You must be cautious about this. It even coerces number string into number and returns true. But a non-number string will return false.**

```
console.log(isFinite(null)); //true
console.log(isFinite('45')); // true
console.log(isFinite('-75')); // true
console.log(isFinite('hello')); //false
```

## Where can you use Infinity?

In his new book JavaScript for impatient programmers, Axel Rauschmayer has an interesting use case for `Infinity`

as a default value. Since `Infinity`

is larger than all numbers, it can be useful in a function that checks for the minimum number in an array:

```
function findMinimum(numbers) {
let min = Infinity;
for (const n of numbers) {
if (n < min) min = n;
}
return min;
}
console.log(findMinimum([20, 6, 90])); // 6
```

This works nicely because `Infinity`

is greater than all numbers so unless all the numbers in the array cross the `Infinity`

threshold, the result won’t have any problems.

## Things to be noted

When working with JSON data, make sure that you are aware of the data that is inside the object before you stringify the JSON object (`JSON.stringify()`

). Take a look at this example.

As you can see, the `Infinity`

values are converted to null when stringifying the JSON object. This would also happen if one of the values was initially `NaN`

.

If I have missed anything, please do let me know in the comments.

Happy Coding!!