README
gulp-ng-lang2js 
A Gulp plugin for use in the build process of AngularJS applications that utilize Angular Translate's asynchronous partial loader feature. Use this plugin to generate one or more language packs to ship with your application, by adding all of the partials for that language to the $translationCache.
Credit
This is a re-purposed version of gulp-ng-html2js by Mark Lagendijk, which I also highly recommend for optimizing your Angular HTML templates. The code is almost identical, so much praise should be sent Mark's way.
Do I Need This?
Do you have an Angular app that uses Angular Translate for i18n?
Yes? Great. You should keep reading.
Let's say you have a modular Angular app with a src directory structure like this:
src
├── index.html
├── app.js
├── view1
│ ├── lang
│ │ ├── de.json
│ │ ├── en.json
│ │ ├── es.json
│ │ └── fr.json
│ ├── view1.css
│ ├── view1.html
│ └── view1.js
└── view2
├── lang
│ ├── de.json
│ ├── en.json
│ ├── es.json
│ └── fr.json
├── view2.css
├── view2.html
└── view2.js
Now let's say you have a build task that copies your language files into a /dist directory like this:
dist
├── index.html
├── app.js
└── i18n
├── view1
│ └── lang
│ ├── de.json
│ ├── en.json
│ ├── es.json
│ └── fr.json
└── view2
└── lang
├── de.json
├── en.json
├── es.json
└── fr.json
You are using the asynchronous partial loader, so your app has a configuration that looks something like this:
angular.module('app', ['pascalprecht.translate'])
.config(translateConfig);
function translateConfig($translateProvider) {
$translateProvider
.fallbackLanguage('en')
.preferredLanguage('en')
.useLoader('$translatePartialLoader', {
urlTemplate: 'i18n/{part}/lang/{lang}.json'
})
.useLoaderCache('$translationCache')
;
}
To avoid the infamous FOUC, you want your application to ship with its default language loaded.
If that all sounds familiar, congratulations! This plugin is for you.
Usage
First, install gulp-ng-lang2js as a development dependency:
npm install --save-dev gulp-ng-lang2js
For best results, you'll also want to install gulp-concat and gulp-jsonminify:
npm install --save-dev gulp-concat gulp-jsonminify
Then, sticking with the example above, add a task like this to your gulpfile.js:
gulp.task('build-translation-cache', buildTranslationCache);
function buildTranslationCache() {
var concat = require('gulp-concat');
var jsonMinify = require('gulp-jsonminify');
var ngLang2Js = require('gulp-ng-lang2js');
return gulp.src('./app/**/en.json')
.pipe(jsonMinify())
.pipe(ngLang2Js({
declareModule: true,
moduleName : 'app.i18n',
prefix : 'i18n/'
}))
.pipe(concat('lang.js'))
.pipe(gulp.dest('./dist/i18n'))
;
}
This would result in a single file being generated in your dist/i18n directory called lang.js that you could load in
your application's index.html file:
<script type="text/javascript" src="app.js"></script>
<script type="text/javascript" src="i18n/lang.js"></script>
You can then include the app.i18n module as a dependency in your app:
angular.module('app', ['pascalprecht.translate', 'app.i18n'])
.config(translateConfig);
function translateConfig($translateProvider) {
$translateProvider
.fallbackLanguage('en')
.preferredLanguage('en')
.useLoader('$translatePartialLoader', {
urlTemplate: 'i18n/{part}/lang/{lang}.json'
})
.useLoaderCache('$translationCache')
;
}
...and you're good to go!
All of the partial files for the language you specified in gulp.src() (**/en.json in this example) have been added
to $translationCache, so your app will not suffer from the FOUC issue and your modular directory structure can remain
in tact.
Bonus Gulp Recipe: Configurable Languages
Want to make your gulp task include one or more languages that can be specified at runtime? Try this:
gulp.task('build-translation-cache', buildTranslationCache);
function buildTranslationCache() {
var concat = require('gulp-concat');
var lang = process.env.LANG || 'en';
var jsonMinify = require('gulp-jsonminify');
var ngLang2Js = require('gulp-ng-lang2js');
return gulp.src('./app/**/{' + lang + '}.json')
.pipe(jsonMinify())
.pipe(ngLang2Js({
declareModule: true,
moduleName : 'app.i18n',
prefix : 'i18n/'
}))
.pipe(concat('lang.js'))
.pipe(gulp.dest('./dist/i18n'))
;
}
Then run the task with the node environment variable LANG set to a comma-separated list of language codes, like this:
LANG='en,sp' gulp build-translation-cache
That would include both English and Spanish languages in the build.
This is great if you want to have your app deployed on different servers for different regions, and want each app server to include a version of the app pre-loaded with the language(s) most commonly used in those regions.
API
ngLang2Js(options)
options.moduleName
Type: String or Function
The name of the generated AngularJS module. Uses the file url if omitted.
When this is a function, the returned value will be the module name. The function will be passed the vinyl file object so the module name can be determined from the path, content, last access time or any other property. Returning undefined will fall back to the file url.
options.declareModule
Type: Boolean
Whether to attempt to declare a new module (used with options.moduleName). True if omitted.
Set this to false if options.moduleName is already declared.
options.prefix
Type: String
The prefix which should be prepended to the file path to generate the file url.
options.stripPrefix
Type: String
The prefix which should be subtracted from the file path to generate the file url.
options.rename
Type: Function
A function that allows the generate file url to be manipulated. For example:
function (translationUrl, translationFile) {
return translationUrl.replace('/lang', '/i18n');
}
options.template
Type: String
A custom Lodash template for generating the Javacript code. The template is called with the following params:
- moduleName: the resulting module name.
- template
- url: the resulting template url.
- content: the JSON content of the input file.
- escapedContent: the escaped JSON content of the input file. Note: the JSON content is escaped for usage in a single quoted string.
- prettyEscapedContent: the readable, escaped JSON content of the input file.
Example
{
translation: "$translationCache.put('<%= translation.url %>', '<%= translation.escapedContent %>');"
}