Here's a small script in Groovy that prints a JSON with all languages codes with their native, English and Portuguese names.
def en = new Locale("en")
def pt = new Locale("pt")
def nameFor(loc, lang) { loc.getDisplayLanguage(lang).replaceAll(/\S+/){ w -> w.toLowerCase().capitalize()} }
println("export default {")
Locale.getISOLanguages().each{
def l = new Locale(it)
println(" $it: {native: '${nameFor(l, l)}', en: '${nameFor(l, en)}', pt: '${nameFor(l, pt)}'},")
}
println("}")
$ groovy langs2json.groovy > languagess.json