This question is about templating and localizing, using require.js and underscore templates through backbone.js. The application will need to be localised on the fly.
Before embarking down a path that later proved problematic, is there a better solution than the one I'm considering - I'm concerned about speed and memory with repeatedly merging and processing the language array. Assume that are a 2-3 thousand language strings.
Current approach (which works, but looks processor heavy):
.
define(['backbone', 'models/model', 'text!template.html', 'i18n!my/nls/translatedbits'],
function(Backbone, MyModel, TemplateText, TranslationObject) {
var View = Backbone.View.extend({
model: {},
initialize : function(params) {
this.model = new MyModel();
},
render : function(callBack) {
// Get the model attributes
var templateParams = _.clone(this.model.attributes);
// Bolt on the tranlsated elements (established from require.js I18N plugin)
templateParams.t = TranslationObject;
// Pass the lot ot the template
var template = _.template(TemplateText, this.model.attributes);
$(this.el).html( template );
return this;
}
});
return View;
}
);
Then the template will read
<%= modelAttribute1 %> <%= t.translationString1 %>
Is there a better solution or a better templating engine? [Better for this purpose - mustache may have other advantages, but can it localize more easily, or can it cache localised results allowing model attributes to be passed in later?]
Note that languages may need to be changed "on the fly" - and that's another concern I have with I18N plugin. I may end up getting the transations by JSON request through a template model but this still requires a merge of objects, which is what I'm trying to avoid.
Here's what I am currently doing (just open-sourced since it seems useful to others)
underi18n is a very minimal lib for doing i18n on templates and code.
It provides:
gettext
catalogs to json format.It does not deal with pluralization.
From the README:
under18n
uses a simple JSON format for catalogs, following the standard gettext
format. In the following example,
{
'Developer': 'Προγραμματιστής',
'Role ${role} does not exist in ${context}': 'Ο ρόλος ${role} δεν υπάρχει στο ${context}'
}
we have two translation strings, the second one with two variables, role
and context
.
A simple python script is provided to help you convert standard .mo
files to this JSON format.
Create a MessageFactory from a json i18n catalog:
var t = underi18n.MessageFactory(catalog);
You can now translate inline:
t('Developer') // returns "Προγραμματιστής"
t('Role ${role} does not exist in ${context}', {role: 'διαχειριστής', context: 'πρόγραμμα'})
// Returns "Ο ρόλος διαχειριστής δεν υπάρχει στο πρόγραμμα"
Typically variables in templates are indicated with some delimiter. In mustache for instance {{ var }}
is used whereas <%= var %>
is default for underscore. We use the same approach to indicate translatable strings. You can specify the delimiters for translatable strings as a RegExp, as well as the left/right delimiters used by your template language of choice in under18n.templateSettings
. By default this is following underscore conventions:
templateSettings: {
translate: /<%_([\s\S]+?)%>/g,
i18nVarLeftDel: '<%=',
i18nVarRightDel: '%>'
}
so, <%_ i18n %>
are set to denote translatable strings and <%= var %>
is used to denote variables inside a template.
You can translate a template by calling under18n.template
, for example using underscore, you can do
var templ = _.template(under18n.template(myTemplate, t));
Given the following catalogs, factories and template for english and greek and assuming an underscore template,
var test_en = {
'files_label': 'Files',
'num_files': 'There are ${num} files in this folder'
},
templ = '<h1><%= title %></h1>' +
'<label><%_ files_label %></label>' +
'<span><%_ num_files %></span>',
t_en = underi18n.MessageFactory(test_en);
t_el = underi18n.MessageFactory(test_el);
the template can by constructed by,
var toRender = _.template(underi18n.template(templ, t_en));
toRender({title: 'Summary', num: 3});
would yield
<h1>Summary</h1>
<label>Files</label>
<span>There are 3 files in this folder</span>
under18n will register as an anonymous module if you use requireJS.
I hope this solves your problem, let me know if not, I was planning to release it at some stage, but hey better now than never ;)
For completeness, the solution that we came up that felt to most optimised was:
When a template was requested from the server, a cookie determined the language and the correct template was delivered.
Used PHP back end to pre-parse the templates; these were then stored in memcached in the correct language
The language template, once requested, was then cached by the browser and internally in a backbone model so it could be rapidly re-used by JavaScript.
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