Simple Translation Resource Lookup - Useful in client side applications

translation.js

var translation = {
	phrases: {
		"vest": {
			"": "Vest",
			"en-GB": "Waistcoat",
			"es": "Chaleco",
			"fr": "Gilet"
		},
	},

	/**
	 * Returns the translation of a given phrase key.
	 * @param {string} key - The key of the translation phrase to look up
	 * @param {string} [language=] - The Language Culture Name of the translation phrase you wish to use; Uses a fall back logic (example: "en-AU" -> "en" -> "")
	 */
	getTranslation: function (key, language) {
		language = language || navigator.language || "";
		
		languageParts = language.split('-');

		if (!translation.phrases[key]) throw `"${key}" not found`;

		return translation.phrases[key][language] ||
			translation.phrases[key][languageParts[0]] ||
			translation.phrases[key][""];
	},
	
	importTranslation: function(language, phrases) {
		for(let phrase in phrases) {
    			if(!translation.phrases.hasOwnProperty(phrase))
				translation.phrases[phrase] = {};
        
			translation.phrases[phrase][language] = phrases[phrase];
		}
	}
}

// example of importing a language (hr-HR.js)
// Croatian - Croatia
translation.importTranslation("hr-HR", {
	"vest": "Prsluk",
	"another key": "..."
});

// test outputs
console.log(translation.getTranslation("vest"));          //Vest
console.log(translation.getTranslation("vest", "en-GB")); //Waistcoat
console.log(translation.getTranslation("vest", "hr-HR")); //Prsluk

console.log(translation.getTranslation("jacket"));        //"jacket" not found