Intl MessageFormat Parser

Parses ICU Message strings into an AST via JavaScript.

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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.

This parser is written in PEG.js, a parser generator for JavaScript.

Usage

import {parse} from 'intl-messageformat-parser';
const ast = parse('this is {count, plural, one{# dog} other{# dogs}}');

Example

import {parse} from 'intl-messageformat-parser';
parse(
`On {takenDate, date, short} <bold>{name}</bold> took {numPhotos, plural,
=0 {no photos.}
=1 {one photo.}
other {# photos.}
}`
);
[
{
"type": 0,
"value": "On "
},
{
"type": 3,
"style": "short",
"value": "takenDate"
},
{
"type": 0,
"value": " "
},
{
"type": 8,
"value": "bold",
"children": [
{
"type": 1,
"value": "name"
}
]
},
{
"type": 0,
"value": " took "
},
{
"type": 6,
"pluralType": "cardinal",
"value": "numPhotos",
"offset": 0,
"options": {
"=0": {
"value": [
{
"type": 0,
"value": "no photos."
}
]
},
"=1": {
"value": [
{
"type": 0,
"value": "one photo."
}
]
},
"other": {
"value": [
{
"type": 7
},
{
"type": 0,
"value": " photos."
}
]
}
}
}
]

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

SymbolMeaningNotes
GEra designator
yyear
Mmonth in year
Lstand-alone month in year
dday in month
Eday of week
elocal day of weeke..eee is not supported
cstand-alone local day of weekc..ccc is not supported
aAM/PM marker
hHour [1-12]
HHour [0-23]
KHour [0-11]
kHour [1-24]
mMinute
sSecond
zTime Zone

Benchmarks

complex_msg AST length 2053
normal_msg AST length 410
simple_msg AST length 79
string_msg AST length 36
complex_msg x 3,926 ops/sec ±2.37% (90 runs sampled)
normal_msg x 27,641 ops/sec ±3.93% (86 runs sampled)
simple_msg x 100,764 ops/sec ±5.35% (79 runs sampled)
string_msg x 120,362 ops/sec ±7.11% (74 runs sampled)