@phensley/messageformat
v1.9.2
Published
Extensible ICU message formatter
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@phensley/messageformat
Compact and extensible ICU message formatter with built-in support for plural
, select
, and selectordinal
. Also supports plural calculations using arbitrary precision decimal numbers.
Installation
NPM:
npm install --save @phensley/messageformat
Yarn:
yarn add @phensley/messageformat
Examples
Setup
The package allows you to wire up the different types how you want. Things are broken out so that parsing can be done separately from evaluation.
Parsing can be done at build time -- read a YAML file, parse messages and embed them into a YAML/JSON file, or embed them into code, for faster runtime message evaluation.
Custom formatting and argument conversion functions can be defined and plugged into the framework.
import { pluralRules } from '@phensley/plurals';
import {
buildMessageMatcher,
parseMessagePattern,
DefaultMessageArgConverter,
MessageArg,
MessageEngine,
MessageFormatter,
MessageNamedArgs
} from '@phensley/messageformat';
const FORMATTERS = {
foo: (args: MessageArg[], options: string[]) =>
options[0] === 'upper' ? args[0].toUpperCase() : args[0].toLowerCase()
};
const FORMATTER_NAMES = Object.keys(FORMATTERS);
const MATCHER = buildMessageMatcher(FORMATTER_NAMES);
const CONVERTER = new DefaultMessageArgConverter();
const parse = (message: string) => parseMessagePattern(message, MATCHER);
const dump = (message: string) => console.log(JSON.stringify(parse(message)));
const plurals = (language: string, region?: string) =>
pluralRules.get(language, region);
const format = (
message: string,
positional: MessageArg[],
named: MessageNamedArgs = {}
) => {
const engine = new MessageEngine(
plurals('en'),
CONVERTER,
FORMATTERS,
parse(message)
);
console.log(engine.evaluate(positional, named));
};
let msg: string;
Example 1 - message parsing (cache for repeated use)
Messages can be pre-parsed and embedded into source code, JSON, or YAML files, or parsed and cached at runtime.
dump('{0 select, male {his} female {her} other {their}} {item}');
[4,[[3,[0],[["male",[0,"his"]],["female",[0,"her"]],["other",[0,"their"]]]],[0," "],[1,"item"]]]
dump('{word} uppercase = {word foo upper} lowercase = {word foo lower}');
[4,[[1,"word"],[0," uppercase = "],[6,"foo",["word"],["upper"]],[0," lowercase = "],[6,"foo",["word"],["lower"]]]]
Example 2 - MessageFormatter class
If you don't need to embed parsed messages into source code, the MessageFormatter
can parse and cache messages at runtime. Internally it uses a least-recently-used cache whose size can be configured. There is no need for the elaborate setup in the first example.
const rules = plurals('en');
const formatter = new MessageFormatter({
plurals: rules,
formatters: FORMATTERS,
cacheSize: 100
});
msg = '{0 select, male {his} female {her} other {their}} {item}';
console.log(formatter.format(msg, ['female'], { item: 'parka' }));
her parka
Example 3 - plural cardinals
msg =
'{count, 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, [], { count: 0 });
format(msg, [], { count: 1 });
format(msg, [], { count: 2 });
format(msg, [], { count: 3 });
Be the first to like this
You liked this
You and someone else liked this
You and 2 others liked this
Example 4 - select
msg = 'Get {0, select, male {his} female {her} other {their}} {item}';
format(msg, ['they'], { item: 'coat' });
format(msg, ['female'], { item: 'jacket' });
format(msg, ['male'], { item: 'parka' });
Get their coat
Get her jacket
Get his parka
Example 5 - plural ordinals and select
msg =
'{name} {tied select true {tied for} other {came in}} {place selectordinal one {#st} ' +
'two {#nd} few {#rd} other {#th}} place';
const racers = [
{ name: 'Lisa', place: 1 },
{ name: 'Bob', place: 2 },
{ name: 'Betty', place: 3 },
{ name: 'Frank', place: 4, tied: true },
{ name: 'George', place: 4, tied: true },
{ name: 'Larry', place: 5 }
];
for (const racer of racers) {
format(msg, [], racer);
}
Lisa came in 1st place
Bob came in 2nd place
Betty came in 3rd place
Frank tied for 4th place
George tied for 4th place
Larry came in 5th place
Example 6 - custom formatter
msg = '{word} uppercase = {word foo upper} lowercase = {word foo lower}';
const WORDS = ['Computer', 'Science', 'Mathematics'];
for (const word of WORDS) {
format(msg, [], { word });
}
Computer uppercase = COMPUTER lowercase = computer
Science uppercase = SCIENCE lowercase = science
Mathematics uppercase = MATHEMATICS lowercase = mathematics