Add Format A Decimal To A Fixed Number Of Digits as a JavaScript TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1325 TILs and counting..._
+_1326 TILs and counting..._
 
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@@ -429,6 +429,7 @@ _1325 TILs and counting..._
 - [Find The Version Of An Installed Dependency](javascript/find-the-version-of-an-installed-dependency.md)
 - [Find Where Yarn Is Installing Binaries](javascript/find-where-yarn-is-installing-binaries.md)
 - [for...in Iterates Over Object Properties](javascript/for-in-iterates-over-object-properties.md)
+- [Format A Decimal To A Fixed Number Of Digits](javascript/format-a-decimal-to-a-fixed-number-of-digits.md)
 - [Formatting Values With Units For Display](javascript/formatting-values-with-units-for-display.md)
 - [Freeze An Object, Sorta](javascript/freeze-an-object-sorta.md)
 - [Generate A V4 UUID In The Browser](javascript/generate-a-v4-uuid-in-the-browser.md)

javascript/format-a-decimal-to-a-fixed-number-of-digits.md

@@ -0,0 +1,52 @@
+# Format A Decimal To A Fixed Number Of Digits
+
+The `Intl.NumberFormat` object is a reliable way to format numbers in an
+i18n-friendly way. It available with Node and all modern browsers.
+
+If I want to format number that I expect to contain decimals, I can do so by
+setting up a formatter using the `decimal` style.
+
+```javascript
+const locale = "en-US";
+const options = {
+  style: "decimal",
+};
+
+const formatter = new Intl.NumberFormat(locale, options);
+
+console.log(formatter.format(1234))
+//=> 1,234
+console.log(formatter.format(1234.5678))
+//=> 1,234.568
+```
+
+Because of my locale (`en-US`), it adds a comma to deliniate the thousandth
+place. By default, it formats to three decimal places excluding decimals
+altogether if it is a whole number.
+
+If I want to specify a fixed number of decimal places including for a whole
+number, I can use the `minimumFractionDigits` and `maximumFractionDigits`
+options.
+
+```javascript
+const locale = "en-US";
+const options = {
+  style: "decimal",
+  minimumFractionDigits: 2,
+  maximumFractionDigits: 2,
+};
+
+const formatter = new Intl.NumberFormat(locale, options);
+
+console.log(formatter.format(1234))
+//=> 1,234.00
+console.log(formatter.format(1234.5678))
+//=> 1,234.57
+```
+
+Here, it includes the `.00` on the whole number and it truncates the number
+with more than 2 decimal places rounding as necessary.
+
+See the [`Intl.NumberFormat`
+docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat)
+for more details.