bower install angular-ngi18n

<script src="dist/angular-ngi18n.js"></script>
...
angular.module('yourApp', ['ngI18n'])
...
.controller('MainCtrl', function ($scope, $i18n) {

(angular-ngi18n.js)
var config = {
    files       : 'i18n/:lang.json',    //Ex : 'i18n/en.json'
    languages   : ['en', 'fr']          //config.languages[0] == default
};

I am 26 years old

<i>{{'how.old.are.you' | i18n:[26]}}</i>

This is the translation of 'key.in.i18n.file' key
<i>{ {'key.in.i18n.file' | i18n} }</i>

{
    ...
    "key.in.i18n.file" : "This is the translation of 'key.in.i18n.file' key",
    ...
}

<form ng-submit="submitForm()">
    <div class="form-group">
        <label for="exampleSelect">{ {'choose.language' | i18n} } :</label>
        <select id="exampleSelect" ng-model="currentLang" ng-change="changeLanguage()">
            <option value="en" selected="selected">English</option>
            <option value="fr" selected="selected">Français</option>
        </select>
    </div>
</form>
...
$scope.currentLang = $i18n.getLanguage();

$scope.changeLanguage = function(){
    $i18n.changeLanguage(this.currentLang);
};