API

Format API

Package

@foo-i18n/t

The format function simply takes an arbitrary string and interpolates it if necessary. If placeholders are found within the string, and values are either missing or misspelled, then TypeScript will provide useful debugging warnings, however the call will not fail.

Declarations

function format(text: string, values?: unknown): string;

Usage

import { format } from '@foo-i18n/t';

console.log(format('{count} messages', { count: 10 }));
// "10 messages"

console.log(format('Hello {name}')); // TS warning
// "Hello ?name"

Extensions

The format function allow features to be added by extending it’s type declaration. For example, the translate API does just that, by adding genders and plurals, for example.

import { format, type FormatText } from '@foo-i18n/t';

export type FormatString = 'Hello {name}' | 'Language : {lang}';

export type FormatValueOptions = {
  indent?: number;
};

// Could either be:
//   FormatText<string, FormatValueOptions>
//   FormatText<FormatString>
//   FormatText<FormatString, FormatValueOptions>
type FormatExt = FormatText<FormatString, FormatValueOptions>;

export const formatExt: FormatExt = (text, ...[values]) => {
  const margin = values?.indent ? ' '.repeat(values?.indent) : '';

  return margin + format(text, values as any);
};

import { formatExt } from './i18n/format-ext.js';

console.log(
  formatExt('Hello {name}', {
    name: 'John',
    indent: 4,
  })
);
// "    Hello John"