To limit decimal places in JavaScript, use the **toFixed()** method by specifying the number of decimal places.

This method:

**Rounds**the number.**Converts**it into a string.**Returns**the number as a string.

For instance, let’s round to 2 decimals:

let pi = 3.1415; let rounded = pi.toFixed(2); console.log(rounded);

Output:

3.14

But this is just one way to do it. Also, it has some caveats.

**This is a comprehensive guide to rounding values in JavaScript**. You will learn how to:

- Round a number with
**toFixed()**method and its caveats. - Round a number using
**Math.round()**function. - Create a generic rounding function.

## 1. Limit Decimal Places Using toFixed() Method

In JavaScript, you can use the built-in **toFixed()** method to limit the decimal places of a number.

For instance, let’s round a number to 2 decimals:

let pi = 3.145; let rounded = pi.toFixed(2); console.log(rounded);

Output:

3.14

**However, sometimes this method does not give accurate results.**

For example, let’s round number **1.0005** to **3** decimals. If you are familiar with mathematics, you know this operation should round the number to **1.001**. But look what happens with the **toFixed()** method:

var n = 1.0005; n = n.toFixed(3); console.log(n);

Output:

1.000

It falsely rounds the number down to **1.000** instead of correctly rounding it up to **1.001**.

Because of this types of inaccuracies, it’s best to use other methods for rounding in JavaScript.

## 2. Limit Decimal Places with Math.round() Function

To limit, that is, round a number to n decimal places, use the built-in **Math.round()** function.

For example, let’s round a number to 2 decimal places.

var n = 2.781; var rounded = Math.round(n * 100) / 100; console.log(rounded);

Output:

2.78

But this approach also has the same caveat as the previous one. Values such as **1.005** get falsely rounded to **1** instead of **1.01**.

For example:

var n = 1.005; var rounded = Math.round(n * 100) / 100; console.log(rounded);

This should produce **1.01** but instead, it returns **1**.

1

To avoid this issue, use the **Number.EPSILON** this way:

var n = 1.005; var rounded = Math.round((n + Number.EPSILON) * 100) / 100; console.log(rounded);

Output:

1.01

## 3. Generic Rounding Function in JavaScript

In the previous example, you learned how to round numbers using **Math.round()** with **number.EPSILON**.

But the example only showed you how to round to 2 decimal places.

What if you want to round to n decimal places?

Let’s write a generic rounding function for that with these specifications:

- To round to 1 decimal, multiply by 10, round, and divide by 10 (
**10^1**). - For 2 decimals multiply and divide by 100 (
**10^2**). - For n decimals, multiply and divide by
**10^n**.

Let’s write a generic rounding function and extend the **Number.prototype** with it. This way you can call** .round()** on any numeric type in JavaScript.

Number.prototype.round = function(n) { const d = Math.pow(10, n); return Math.round((this + Number.EPSILON) * d) / d; }

Example use:

1.005.round(2) // Returns 1.01 1.22.round(0) // Returns 1

Notice how this will also result in problems when rounding numbers close to the built-in floating-point accuracy.

For instance:

1.32.round(16) // Returns 1.3200000000000003

## Conclusion

Today, you learned how to limit decimal places in JavaScript.

To recap, you can use the **.toFixed()** method to limit decimal places. But this has some rounding issues. To overcome those, you can use **Math.round()** with **number.EPSILON**.

Thanks for reading.

Happy coding!