The formatToParts()
method of Intl.NumberFormat
instances allows locale-aware formatting of strings produced by this Intl.NumberFormat
object.
The formatToParts()
method of Intl.NumberFormat
instances allows locale-aware formatting of strings produced by this Intl.NumberFormat
object.
formatToParts() formatToParts(number)
An Array
of objects containing the formatted number in parts.
The formatToParts()
method is useful for custom formatting of number strings. It returns an Array
of objects containing the locale-specific tokens from which it possible to build custom strings while preserving the locale-specific parts. The structure the formatToParts()
method returns, looks like this:
[ { type: "integer", value: "3" }, { type: "group", value: "." }, { type: "integer", value: "500" }, ];
Possible types are the following:
compact
The exponent in "long"
or "short"
form, depending on how compactDisplay
(which defaults to short
) is specified when notation
is set to compact
.
currency
The currency string, such as the symbols "$" and "€" or the name "Dollar", "Euro", depending on how currencyDisplay
is specified.
decimal
The decimal separator string (".").
exponentInteger
The exponent integer value, when notation
is set to scientific
or engineering
.
exponentMinusSign
The exponent minus sign string ("-").
exponentSeparator
The exponent separator, when notation
is set to scientific
or engineering
.
fraction
The fraction number.
group
The group separator string (",").
infinity
The Infinity
string ("∞").
integer
The integer number.
literal
Any literal strings or whitespace in the formatted number.
minusSign
The minus sign string ("-").
nan
The NaN
string ("NaN").
plusSign
The plus sign string ("+").
percentSign
The percent sign string ("%").
unit
The unit string, such as the "l" or "litres", depending on how unitDisplay
is specified.
unknown
The string for unknown
type results.
NumberFormat
outputs localized, opaque strings that cannot be manipulated directly:
const number = 3500; const formatter = new Intl.NumberFormat("de-DE", { style: "currency", currency: "EUR", }); formatter.format(number); // "3.500,00 €"
However, in many User Interfaces there is a desire to customize the formatting of this string. The formatToParts
method enables locale-aware formatting of strings produced by NumberFormat
formatters by providing you the string in parts:
formatter.formatToParts(number); // return value: [ { type: "integer", value: "3" }, { type: "group", value: "." }, { type: "integer", value: "500" }, { type: "decimal", value: "," }, { type: "fraction", value: "00" }, { type: "literal", value: " " }, { type: "currency", value: "€" }, ];
Now the information is available separately and it can be formatted and concatenated again in a customized way. For example by using Array.prototype.map()
, arrow functions, a switch statement, template literals, and Array.prototype.reduce()
.
const numberString = formatter .formatToParts(number) .map(({ type, value }) => { switch (type) { case "currency": return `<strong>${value}</strong>`; default: return value; } }) .reduce((string, part) => string + part);
This will make the currency bold, when using the formatToParts()
method.
console.log(numberString); // "3.500,00 <strong>€</strong>"
Specification |
---|
ECMAScript Internationalization API Specification # sec-intl.numberformat.prototype.formattoparts |
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | Deno | Node.js | ||
formatToParts |
64 | 12 | 58 | 51 | 13 | 64 | 58 | 47 | 13 | 9.0 | 64 | 1.8 | 10.0.0Before version 13.0.0, only the locale data foren-US is available by default. See the NumberFormat() constructor for more details. |
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/formatToParts