Parses ICU Message strings into an AST via JavaScript.

Overview#

This package implements a parser in JavaScript that parses the industry standard ICU Message strings — used for internationalization — into an AST. The produced AST can then be used by a compiler, like intl-messageformat, to produce localized formatted strings for display to users.

The parser detects Unicode property escape support at startup and falls back to generated character ranges when unavailable. No regex polyfill is required for identifier parsing.

Usage#

const ast = parse(`this is {count, plural,
  one{# dog}
  other{# dogs}
}`)

Example#

<pre>
  {JSON.stringify(
    IcuMessageFormatParser.parse(
      `On {takenDate, date, short} <bold>{name}</bold> took {numPhotos, plural,
          =0 {no photos.}
          =1 {one photo.}
          other {# photos.}
        }`
    ),
    undefined,
    2
  )}
</pre>

Supported DateTime Skeleton#

ICU provides a wide array of pattern to customize date time format. However, not all of them are available via ECMA402's Intl API. Therefore, our parser only support the following patterns

With a locale parse option, j uses the locale’s preferred hour cycle. Explicit hourCycle options and u-hc extensions take precedence. The parser supports both Intl.Locale.getHourCycles() and the legacy hourCycles property.

Benchmarks#

complex_msg AST length 10861
normal_msg AST length 1665
simple_msg AST length 364
string_msg AST length 131

complex_msg x 29,940 ops/sec ±1.23% (89 runs sampled)
normal_msg x 253,612 ops/sec ±1.01% (92 runs sampled)
simple_msg x 1,805,642 ops/sec ±0.70% (94 runs sampled)
string_msg x 2,694,133 ops/sec ±1.05% (95 runs sampled)