javascript instance method
Intl.RelativeTimeFormat.prototype.formatToParts()
The formatToParts() method of RelativeTimeFormat instances returns an array of objects representing each part of the formatted string that would be returned by format(). It is useful for building custom strings from the locale-specific tokens.
const rtf = new Intl.RelativeTimeFormat("en", { numeric: "auto" });
const parts = rtf.formatToParts(10, "seconds");
console.log(parts[0].value);
// Expected output: "in "
console.log(parts[1].value);
// Expected output: "10"
console.log(parts[2].value);
// Expected output: " seconds"
Syntax
formatToParts(value, unit)
Parameters
value- : Numeric value to use in the internationalized relative time message.
unit- : Unit to use in the relative time internationalized message. Possible values are:
"year","quarter","month","week","day","hour","minute","second". Plural forms are also permitted.
- : Unit to use in the relative time internationalized message. Possible values are:
Return value
An Array of objects containing the formatted relative time in parts. Each object has two or three properties, type, value, and optionally unit, each containing a string. The string concatenation of value, in the order provided, will result in the same string as format(). The parts can be thought of as directly obtained from calling Intl.NumberFormat.prototype.formatToParts() with the numeric value, passing only the numberingSystem option, and then adding additional type: "literal" tokens, such as "in ", " days ago", etc. All tokens that are produced by the NumberFormat have an additional unit property, which is the singular form of the input unit; this is for programmatic usage and is not localized. The localized unit is output as a part of a literal token.
When options.numeric is "auto", and there’s a special string for the value, the returned array is a single literal token.
Examples
Using formatToParts()
const rtf = new Intl.RelativeTimeFormat("en", { numeric: "auto" });
// Format relative time using the day unit
rtf.formatToParts(-1, "day");
// [{ type: "literal", value: "yesterday"}]
rtf.formatToParts(100, "day");
// [
// { type: "literal", value: "in " },
// { type: "integer", value: "100", unit: "day" },
// { type: "literal", value: " days" }
// ]