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Intl 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.
This parser is written in PEG.js, a parser generator for JavaScript. This parser's implementation was inspired by and derived from Alex Sexton's messageformat.js project. The differences from Alex's implementation are:
- This project is standalone.
- It's authored as ES6 modules compiled to CommonJS and the Bundle format for the browser.
- The produced AST is more descriptive and uses recursive structures.
- The keywords used in the AST match the ICU Message "spec".
Usage
Loading in the Browser
The dist/ folder contains the version of this package for use in the browser, and it can be loaded and used like this:
<script src="intl-messageformat-parser/dist/parser.min.js"></script>
<script>
IntlMessageFormatParser.parse('...');
</script>
Loading in Node.js
This package can also be require()-ed in Node.js:
var parser = require('intl-messageformat-parser');
parser.parse('...');
Example
Given an ICU Message string like this:
On {takenDate, date, short} {name} took {numPhotos, plural,
=0 {no photos.}
=1 {one photo.}
other {# photos.}
}
// Assume `msg` is the string above.
parser.parse(msg);
This parser will produce this AST:
{
"type": "messageFormatPattern",
"elements": [
{
"type": "messageTextElement",
"value": "On "
},
{
"type": "argumentElement",
"id": "takenDate",
"format": {
"type": "dateFormat",
"style": "short"
}
},
{
"type": "messageTextElement",
"value": " "
},
{
"type": "argumentElement",
"id": "name",
"format": null
},
{
"type": "messageTextElement",
"value": " took "
},
{
"type": "argumentElement",
"id": "numPhotos",
"format": {
"type": "pluralFormat",
"offset": 0,
"options": [
{
"type": "optionalFormatPattern",
"selector": "=0",
"value": {
"type": "messageFormatPattern",
"elements": [
{
"type": "messageTextElement",
"value": "no photos."
}
]
}
},
{
"type": "optionalFormatPattern",
"selector": "=1",
"value": {
"type": "messageFormatPattern",
"elements": [
{
"type": "messageTextElement",
"value": "one photo."
}
]
}
},
{
"type": "optionalFormatPattern",
"selector": "other",
"value": {
"type": "messageFormatPattern",
"elements": [
{
"type": "messageTextElement",
"value": "# photos."
}
]
}
}
]
}
}
]
}
License
This software is free to use under the Yahoo! Inc. BSD license. See the LICENSE file for license text and copyright information.
