ICU MessageFormat Parser

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.

Usage

import {parse} from '@formatjs/icu-messageformat-parser'
const ast = parse(`this is {count, plural, 
  one{# dog} 
  other{# dogs}
}`)

Example

Live Editor

<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>

<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>

Result

[
  {
    "type": 0,
    "value": "On "
  },
  {
    "type": 3,
    "value": "takenDate",
    "style": "short"
  },
  {
    "type": 0,
    "value": " "
  },
  {
    "type": 8,
    "value": "bold",
    "children": [
      {
        "type": 1,
        "value": "name"
      }
    ]
  },
  {
    "type": 0,
    "value": " took "
  },
  {
    "type": 6,
    "value": "numPhotos",
    "options": {
      "=0": {
        "value": [
          {
            "type": 0,
            "value": "no photos."
          }
        ]
      },
      "=1": {
        "value": [
          {
            "type": 0,
            "value": "one photo."
          }
        ]
      },
      "other": {
        "value": [
          {
            "type": 7
          },
          {
            "type": 0,
            "value": " photos."
          }
        ]
      }
    },
    "offset": 0,
    "pluralType": "cardinal"
  }
]

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

Symbol	Meaning	Notes
G	Era designator
y	year
M	month in year
L	stand-alone month in year
d	day in month
E	day of week
e	local day of week	e..eee is not supported
c	stand-alone local day of week	c..ccc is not supported
a	AM/PM marker
h	Hour [1-12]
H	Hour [0-23]
K	Hour [0-11]
k	Hour [1-24]
m	Minute
s	Second
z	Time Zone

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)