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

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

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+# 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.