format-num.js…or ES6!

This is a quick tip post, but there's a tonne of "cool" syntax features in ES6, but when you dig around a little more you'll find a few nicities knocking around (which I tend to find by playing in devtools' console).

I was recently working on a node based project which needed to format a number from 1600.6666 to £1,600.67. Initially I went spelunking for a npm package that did the job for me. I found format.js and numeral.js…and quite a number of other options.

But why add another library to my code, when I can use ES6?

toLocaleString(…)

Enter toLocaleString with powerups! Firstly, the function is available on a few prototype chains, including String and Number. We want the the Number (i.e. "1000".toLocaleString() doesn't do want we want).

Let's take a look (or play with this bin):

// => 1,600.667
(1600.666666).toLocaleString();

// => 1.600,667
(1600.666666).toLocaleString('de-DE');

// => 1,600.67
(1600.666666).toLocaleString('gb-GB', {
  minimumFractionDigits: 2,
  maximumFractionDigits: 2
});

// => 1,600.00
(1600).toLocaleString('gb-GB', {
  minimumFractionDigits: 2,
  maximumFractionDigits: 2
});

So now instead of messing around with Math.round or .toFixed, if I have support for toLocaleString, then I'll use it for perfect formating.