MessageEngine

Evalutes a parsed message against one or more arguments.

new

Constructs a new message engine.

Syntax

new MessageEngine(plurals, converters, formatters, code)

Parameters

• plurals: PluralRules
  • A set of plural rules for a given locale
• converter: MessageArgConverter
  • Converts arguments to required types. See DefaultMessageArgConverter
• formatters: MessageFormatFuncMap
  • An object whose properties are message format functions.
• code: MessageCode
  • A parsed message.

evaluate

Evaluate a parsed message against one or more arguments. Arguments can be positional or named.

Syntax

evaluate(positional: MessageArg[], named: MessageNamedArgs): string

Parameters

• positional: MessageArg[]
  • Arguments keyed by their position in the array
• named: MessageNamedArgs
  • Arguments keyed by name

Example

import {
  buildMessageMatcher,
  parseMessagePattern,
  DefaultMessageArgConverter,
  MessageArg,
  MessageEngine,
  MessageNamedArgs
} from '@phensley/messageformat';
import { pluralRules } from '@phensley/plurals';

const FORMATTERS = {
  foo: (args: MessageArg[], options: string[]) =>
    options[0] === 'upper' ? args[0].toUpperCase() : args[1].toLowerCase()
};
const NAMES = Object.keys(FORMATTERS);
const MATCHER = buildMessageMatcher(NAMES);
const CONVERTER = new DefaultMessageArgConverter();

const parse = (message: string) => parseMessagePattern(message, MATCHER);

const format = (
  message: string,
  positional: MessageArg[],
  named: MessageNamedArgs = {}
) => {
  const plurals = pluralRules.get('en');
  const engine = new MessageEngine(
    plurals,
    CONVERTER,
    FORMATTERS,
    parse(message)
  );
  log(engine.evaluate(positional, named));
};

const msg =
  '{0, plural, offset:1 =0 {Be the first to like this} =1 {You liked this} ' +
  'one {You and someone else liked this} other {You and # others liked this}}';

format(msg, [0]);
format(msg, [1]);
format(msg, [2]);
format(msg, [3]);

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