Using numeric separators for better readability in vanilla JS

This week, we’ve looked at how to format numbers into strings, and how to format numbers as currency.

Today, we’re going to wrap things up by looking at a simple trick for making big numbers easier to read in your code with the numeric separator.

Let’s imagine you have a really big number, like this.

let num = 1234567890987654321;

Because it’s a number and not a string, you can’t add commas (or dots, depending on where you live) as “thousands” indicators.

// THIS THROWS AN ERROR
let num = 1,234,567,890,987,654,321;

However, modern JavaScript gives us the numeric seperator, an underscore (_) placed between numeric characters in a number to make it easier to read.

let num = 1_234_567_890_987_654_321;

Numeric separators make big numbers easier to read, but are ignored by all of the Number object functions and operators.

For example, you could still do something like this.

// returns 1234567890.9876544
let smallNum = num / 1_000_000_000;