import { isLanguageCode } from "https://deno.land/x/iso639_1@1.2.20090901/mod.ts";
A predicate function to narrow down the string type to the LanguageCode type if the given string is a valid language code.
const code: string | null = prompt("Enter a two-letter language code:");
if (isLanguageCode(code)) {
// code is now narrowed down to LanguageCode
console.log("The language you chose is", authoritativeLabels[code].en);
}
Returns
code is LanguageCode
true
if the given string is a valid language code, false
.