Formatting percentage values with JavaScript Intl

Javascript contains an Internationalisation API that you can use to format numbers to a user's locale. Setting the style to percent is all that is needed.

1Intl.NumberFormat("en-GB", { style: "percent"}).format(1.2345); // => "123%" 

Note: A value of 1 will return 100% because 1x anything is 100%!

To specify the decimal places use minimumFractionDigits and maximumFractionDigits to give you more visual control.

1Intl.NumberFormat("en-GB", { 
2  style: "percent", 
3  minimumFractionDigits: 1, 
4  maximumFractionDigits: 2
5}).format(123.45); // => "123.45%" 

This can all be wrapped in a function to save repetition and keep consistency across your app.

1const formatPercentage = (value, locale = "en-GB") => {
2    return Intl.NumberFormat(locale, {
3        style: "percent",
4        minimumFractionDigits: 1,
5        maximumFractionDigits: 2
6    }).format(value);
7};
8
9formatPercentage(1); 		// => "100.0%"
10formatPercentage(0.1); 		// => "10.0%"
11formatPercentage(0.13); 	// => "13.0%"
12formatPercentage(0.135); 	// => "13.5%"
13formatPercentage(0.1357); 	// => "13.57%"
14formatPercentage(0.13579); 	// => "13.58%"