# The Number toExponential() method

> Learn how the JavaScript Number toExponential() method returns a string with the number in exponential notation, and how to set the fractional part digits.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2019-03-22 | Topics: [JavaScript](https://flaviocopes.com/tags/js/) | Canonical: https://flaviocopes.com/javascript-number-toexponential/

You can use this method to get a string representing the number in exponential notation:

```js
new Number(10).toExponential() //1e+1 (= 1 * 10^1)
new Number(21.2).toExponential() //2.12e+1 (= 2.12 * 10^1)
```

You can pass an argument to specify the fractional part digits:

```js
new Number(21.2).toExponential(1) //2.1e+1
new Number(21.2).toExponential(5) //2.12000e+1
```

Notice how we lost precision in the first example.