MessageFormatClassic

The MessageFormatClassic API adopts the classic ICU MessageFormat patterns for formatting messages.

The MessageFormatClassic API supports both named-argument style and numbered-argument style in patterns. Use the named-argument style to improve readability for developers and translators by providing descriptively named arguments. In addition, that can better infer what kind of values go into the arguments in a pattern.

Constructors

new MessageFormatClassic()

new MessageFormatClassic(): MessageFormatClassic

Returns

MessageFormatClassic

Methods

format()

static format(pattern: string, args: Map<string, string | number | Date>): string | null

Formats the specified pattern with named arguments in the default locale.

Parameters

pattern

string

A classic message format pattern.

args

Map<string, string | number | Date>

Map of argument names to their values. Formatted message on success, null on failure.

Returns

string | null

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formatPositional()

static formatPositional(pattern: string, args?: (string | number | Date)[]): string | null

Formats the specified pattern with numbered arguments in the default locale.

Parameters

pattern

string

A classic message format pattern.

args?

(string | number | Date)[]

Array of argument values Formatted message on success, null on failure.

Returns

string | null

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formatPositionalWithLocale()

static formatPositionalWithLocale(pattern: string, locale: string | null, args?: (string | number | Date)[]): string | null

Formats the specified pattern with numbered arguments in the specified locale.

Parameters

pattern

string

A classic message format pattern.

locale

string | null

A BCP-47 locale string. If this parameter is null or an empty string, the default locale is used.

args?

(string | number | Date)[]

Array of argument values Formatted message on success, null on failure.

Returns

string | null

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formatWithLocale()

static formatWithLocale(pattern: string, locale: string | null, args: Map<string, string | number | Date>): string | null

Formats the specified pattern with named arguments in the specified locale.

Parameters

pattern

string

A classic message format pattern.

locale

string | null

A BCP-47 locale string. If this parameter is null or an empty string, the default locale is used.

args

Map<string, string | number | Date>

Map of argument names to their values. Formatted message on success, null on failure.

Returns

string | null

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getMajorVersion()

static getMajorVersion(): number

Gets the major version number. Major version number.

Returns

number

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getMinorVersion()

static getMinorVersion(): number

Gets the minor version number. Minor version number.

Returns

number

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getPatchVersion()

static getPatchVersion(): number

Gets the patch version number. Patch version number.

Returns

number

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Last updated: Jul 22, 2026