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    1.0.0-rc-2 • Public • Published


    Handlebars helpers for internationalization.

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    • Integrate internationalization features with Handlebars to lower the barrier for localizing Handlebars templates.

    • Build on current and emerging JavaScript Intl standards — architect in a future-focused way.

    • Run in both Node.js and in the browser with a single <script> element.

    How It Works

    Template Source:

    <b>Price:</b> {{formatNumber price style="currency" currency="USD"}}

    Render Template:

    var intlData = {
        locales: 'en-US'
    var context = {
        price: 1000
    var html = template(context, {
        data: {intl: intlData}


    <b>Price:</b> $1,000.00


    • Formats numbers and dates/times, including those in complex messages using the JavaScript built-ins: Intl.NumberFormat and Intl.DateTimeFormat, respectively.

    • Formats complex messages, including plural and select arguments using the Intl MessageFormat library which follows ICU Message and CLDR standards.

    • Supports formatting message strings that contain HTML via the {{formatHTMLMessage}} helper.


    Intl Dependency

    This package assumes that the Intl global object exists in the runtime. Intl is present in all modern browsers except Safari, and there's work happening to integrate Intl into Node.js.

    Luckly, there's the Intl.js polyfill! You will need to conditionally load the polyfill if you want to support runtimes which Intl is not already built-in.

    Registering Helpers in a Browser

    First, load Handlebars and this package onto the page:

    <script src="handlebars.js"></script>
    <script src="handlebars-helper-intl.js"></script>

    Then, register the helpers with Handlebars:


    This package will create the HandlebarsIntl global that has the registerWith() function.

    Registering Helpers in Node.js

    Import Handlebars and this package, then register the Intl helpers with Handlebars:

    var Handlebars     = require('handlebars'),
        HandlebarsIntl = require('handlebars-helper-intl');

    Supplying i18n Data to Handlebars

    Handlebars has a data channel feature which is separate from the context a template is rendered with — it provides a side channel in which the data is piped through the template to all helpers and partials. This package uses this data channel to provide the i18n used by the helpers.


    A string with a BCP 47 language tag, or an array of such strings; e.g., "en-US". If you do not provide a locale, the default locale will be used, but you should always provide one!

    This value is used by the helpers when constructing the underlying formatters.


    Any arbitrary data can be provided on the data.intl object; one common use is to use it hold complex message strings.

    Note: These messages need to follow the ICU Message standard. Luckily this is a common standard that professional translators should already be familiar with.

    // Static collection of messages, per-locale.
    var MESSAGES = {
        foo: '{hostName} hosted the party!',
        bar: 'Pets? We have: {numPets, number, integer}',

    These statically defined message strings can be provided to handlebars via data.intl.messages:

    var intlData = {
        locales : 'en-US',
        messages: MESSAGES
    var context = {...};
    // Supply the `intl` `data` object when rendering the template.
    var html = template(context, {
        data: {intl: intlData}


    Object with user defined options for format styles. This is used to supply custom format styles and is useful you need supply a set of options to the underlying formatter; e.g., outputting a number in USD:

        number: {
            USD: {
                style   : 'currency',
                currency: 'USD'
        date: {...},
        time: {...}

    These pre-defined formats map to their respective helpers of the same type, and all data.intl.formats are used by the {{formatMessage}} and {{formatHTMLMessage}} helpers. They can then be used by String name/path like this:

    {{formatNumber 100 "USD"}}



    Block helper used to create a new intl data scope by updating the i18n data supplied to Handlebars within the block. This is useful when you need to render part of the page in a particular locale, or need to supply the i18n data to Handlebars via the template context — some Handlebars integrations might not support supplying when rendering.

    The following example uses {{#intl}} to set the locale to French and will output "1 000":

    {{#intl locales="fr-FR"}}
        {{formatNumber 1000}}


    Utility helper for accessing and returning the value the properties from the i18n data supplied to Handlebars via a string namespace. This provides descriptive error messages when accessing a property that is undefined, unlike Handlebars built-in data channel access syntax @.

    The following are equivalent, both lookup the FOO message from data.intl.messages.FOO:

    {{formatMessage (intlGet "messages.FOO")}}
    {{formatMessage @intl.messages.FOO}}


    • namespace: String namespace to lookup a value on the data.intl object.


    Formats dates using Intl.DateTimeFormat, and returns the formatted string value.

    {{formatDate now weekday="long" timeZone="UTC"}}
    var intlData = {locales: 'en-US'};
    var html = template({now:}, {
        data: {intl: intlData}
    console.log(html); // => "Tuesday, August 12, 2014"


    • date: Date instance or String timestamp to format.

    • [format]: Optional String path to a predefined format on data.intl.formats. The format's values are merged with any hash argument values.

    Hash Arguments:

    The hash arguments passed to this helper become the options parameter value when the Intl.DateTimeFormat instance is created.


    This delegates to the {{formatDate}} helper, but first it will reference any String named format from data.intl.formats.time.


    Formats numbers using Intl.NumberFormat, and returns the formatted string value.

    {{formatNumber price style="currency" currency="USD"}}
    var intlData = {locales: 'en-US'};
    var html = template({price: 100}, {
        data: {intl: intlData}
    console.log(html); // => "$100.00"


    • number: Number to format.

    • [format]: Optional String path to a predefined format on data.intl.formats. The format's values are merged with any hash argument values.

    Hash Arguments:

    The hash arguments passed to this helper become the options parameter value when the Intl.NumberFormat instance is created.


    Formats ICU Message strings with the given values supplied as the hash arguments.

    You have {numPhotos, plural,
        0= {no photos.}
        1= {one photo.}
        other {# photos.}}
    {{formatMessage (intlGet "") numPhotos=numPhotos}}
    var MESSAGES = {
        photos: '...', // String from code block above.
    var intlData = {
        locales : 'en-US',
        messages: MESSAGES
    var html = template({numPhotos: 1}, {
        data: {intl: inltData}
    console.log(html); // => "You have one photo."


    • message: String message or IntlMessageFormat instance to format with the given hash arguments as the values.

      Note: It is recommended to access the message from the i18n data supplied to Handlebars using the {{intlGet}} helper or @intl-data syntax, instead of including the literal message string in the template.

    Hash Arguments:

    The hash arguments represent the name/value pairs that are used to format the message by providing values for its argument placeholders.


    This delegates to the {{formatMessage}} helper, but will first HTML-escape all of the hash argument values. This allows the message string to contain HTML and it will be considered safe since it's part of the template and not user-supplied data.

    Note: The recommendation is to remove all HTML from message strings, but sometimes it can be impractical, in those cases, this helper can be used.


    This software is free to use under the Yahoo! Inc. BSD license. See the LICENSE file for license text and copyright information.


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