---
title: Number.prototype.toExponential()
short-title: toExponential()
slug: Web/JavaScript/Reference/Global_Objects/Number/toExponential
page-type: javascript-instance-method
browser-compat: javascript.builtins.Number.toExponential
sidebar: jsref
---

The **`toExponential()`** method of {{jsxref("Number")}} values returns a string representing
this number in exponential notation.

{{InteractiveExample("JavaScript Demo: Number.prototype.toExponential()")}}

```js interactive-example
function expo(x, f) {
  return Number.parseFloat(x).toExponential(f);
}

console.log(expo(123456, 2));
// Expected output: "1.23e+5"

console.log(expo("123456"));
// Expected output: "1.23456e+5"

console.log(expo("oink"));
// Expected output: "NaN"
```

## Syntax

```js-nolint
toExponential()
toExponential(fractionDigits)
```

### Parameters

- `fractionDigits` {{optional_inline}}
  - : Optional. An integer specifying the number of digits after the decimal point.
    Defaults to as many digits as necessary to specify the number.

### Return value

A string representing the given {{jsxref("Number")}} object in exponential notation
with one digit before the decimal point, rounded to
`fractionDigits` digits after the decimal point.

### Exceptions

- {{jsxref("RangeError")}}
  - : Thrown if `fractionDigits` is not between `0` and `100` (inclusive).
- {{jsxref("TypeError")}}
  - : Thrown if this method is invoked on an object that is not a {{jsxref("Number")}}.

## Description

If the `fractionDigits` argument is omitted, the number of digits
after the decimal point defaults to the number of digits necessary to represent the
value uniquely.

If you use the `toExponential()` method for a numeric literal and the
numeric literal has no exponent and no decimal point, leave whitespace(s) before the dot
that precedes the method call to prevent the dot from being interpreted as a decimal
point.

If a number has more digits than requested by the
`fractionDigits` parameter, the number is rounded to the nearest
number represented by `fractionDigits` digits. See the discussion
of rounding in the description of the {{jsxref("Number/toFixed", "toFixed()")}} method, which also applies to `toExponential()`.

## Examples

### Using toExponential

```js
const numObj = 77.1234;

console.log(numObj.toExponential()); // 7.71234e+1
console.log(numObj.toExponential(4)); // 7.7123e+1
console.log(numObj.toExponential(2)); // 7.71e+1
console.log((77.1234).toExponential()); // 7.71234e+1
console.log((77).toExponential()); // 7.7e+1
```

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [Polyfill of `Number.prototype.toExponential` with many bug fixes in `core-js`](https://github.com/zloirock/core-js#ecmascript-number)
- [es-shims polyfill of `Number.prototype.toExponential`](https://www.npmjs.com/package/number.prototype.toexponential)
- {{jsxref("Number.prototype.toFixed()")}}
- {{jsxref("Number.prototype.toPrecision()")}}
- {{jsxref("Number.prototype.toString()")}}