i18n.js

    // ES5 way
    t: function () {
			let key = _.first(arguments);
			let replacements = _.rest(arguments);
			let translation = translations[key];

			if (translation && replacements.length) {
				translation = format.apply(null, [translation].concat(replacements));
			}

			return translation || key;
		}

    // ES6 way
		t: function (key, ...replacements) {
			let translation = translations[key];

			if (translation && replacements.length) {
				translation = format.apply(null, [translation].concat(replacements));
			}

			return translation || key;
		}