Intl.RelativeTimeFormat

The Intl.RelativeTimeFormat object is a constructor for objects that enable language-sensitive relative time formatting.

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Syntax

new Intl.RelativeTimeFormat([locales[, options]]) 

Parameters

locales

Optional. A string with a BCP 47 language tag, or an array of such strings. For the general form and interpretation of the locales argument, see the Intl page.

options

Optional. An object with some or all of the following properties:

• localeMatcher
  The locale matching algorithm to use. Possible values are "lookup" and "best fit"; the default is "best fit". For information about this option, see Intl.
• numeric
  The format of output message. Possible values are:
  • "always" (default, e.g., 1 day ago),
  • or "auto" (e.g., yesterday). The "auto" value allows to not always have to use numeric values in the output.
• style
  The length of the internationalized message. Possible values are:
  • "long" (default, e.g., in 1 month)
  • "short" (e.g., in 1 mo.),
  • or "narrow" (e.g., in 1 mo.). The narrow style could be similar to the short style for some locales.

Description

Properties

Intl.RelativeTimeFormat.prototype

Allows the addition of properties to all objects.

Methods

Intl.RelativeTimeFormat.supportedLocalesOf()

Returns an array containing those of the provided locales that are supported without having to fall back to the runtime's default locale.

RelativeTimeFormat instances

Properties

RelativeTimeFormat instances inherit the following properties from their prototype:

Intl.RelativeTimeFormat.prototype.constructor

A reference to Intl.RelativeTimeFormat.

Methods

RelativeTimeFormat instances inherit the following methods from their prototype:

Intl.RelativeTimeFormat.prototype.format()

Formats a value and a unit according to the locale and formatting options of the given Intl.RelativeTimeFormat object.

Intl.RelativeTimeFormat.prototype.formatToParts()

Returns an Array of objects representing the relative time format in parts that can be used for custom locale-aware formatting.

Intl.RelativeTimeFormat.prototype.resolvedOptions()

Returns a new object with properties reflecting the locale and formatting options computed during initialization of the object.

Examples

Basic format usage

The following example shows how to create a relative time formatter using the English language.

// Create a relative time formatter in your locale
// with default values explicitly passed in.
const rtf = new Intl.RelativeTimeFormat("en", {
    localeMatcher: "best fit", // other values: "lookup"
    numeric: "always", // other values: "auto"
    style: "long", // other values: "short" or "narrow"
});

// Format relative time using negative value (-1).
rtf.format(-1, "day");
// > "1 day ago"

// Format relative time using positive  value (1).
rtf.format(1, "day");
// > "in 1 day"

Using the auto option

If numeric:auto option is passed, it will produce the string yesterday or tomorrow instead of 1 day ago or in 1 day. This allows to not always have to use numeric values in the output.

// Create a relative time formatter in your locale
// with numeric: "auto" option value passed in.
const rtf = new Intl.RelativeTimeFormat("en", { numeric: "auto" });

// Format relative time using negative value (-1).
rtf.format(-1, "day");
// > "yesterday"

// Format relative time using positive day unit (1).
rtf.format(1, "day");
// > "tomorrow"

Using formatToParts

The following example shows how to create a relative time formatter returning formatted parts

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" }]

Specifications

Browser compatibility