Lookup

@localizer/format-lookup 1.0.1

preview

lookupFormatter<T> ( lut ): ValueFormatter<T>

• T - The type of value to format. This formatter ensures type safety and simplifies handling of unconventional value types.

Look-up table

The formatter uses a look-up table (lut) to map keys to values. Keys can be strings, numbers, or special symbols for null, undefined, or both. Values can be Localizable items or value formatters.

This formatter works like a JavaScript switch statement but with a cleaner, more compact syntax.

lut Key	lut Value	Condition
number or string	A localizable value or a formatter used to format the value.	When the formatter argument matches the key.
[UndefinedValue]	A localizable value.	When undefined is passed to the formatter.
[NullValue]	A localizable value.	When null is passed to the formatter.
[NoValue]	A localizable value.	When either undefined or null is passed to the formatter.
[DefaultValue]	A localizable value or a formatter used to format the value.	When none of the other conditions are met.

Typical use

This formatter is ideal for formatting enum-like values, mapping predefined keys to localized strings or custom formatting logic.

import { lookupFormatter } from '@localizer/format-lookup';
import { translations } from './translations.js';

const lookupTable = {
  UPLOAD: translations.upload,
  DOWNLOAD: translations.download,
} as const;

export type Direction = keyof typeof lookupTable;

export const directionFormatter = lookupFormatter<Direction>(lookupTable);