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get_charset.ts
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get_charset.ts
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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
import { parseMediaType } from "./parse_media_type.ts";
import { type DBEntry } from "./_util.ts";
import { db, type KeyOfDb } from "./_db.ts";
/**
* Given a media type or header value, identify the encoding charset. If the
* charset cannot be determined, the function returns `undefined`.
*
* @example
* ```ts
* import { getCharset } from "https://deno.land/std@$STD_VERSION/media_types/get_charset.ts";
*
* getCharset("text/plain"); // `UTF-8`
* getCharset("application/foo"); // undefined
* getCharset("application/news-checkgroups"); // `US-ASCII`
* getCharset("application/news-checkgroups; charset=UTF-8"); // `UTF-8`
* ```
*/
export function getCharset(type: string): string | undefined {
try {
const [mediaType, params] = parseMediaType(type);
if (params && params["charset"]) {
return params["charset"];
}
const entry = db[mediaType as KeyOfDb] as DBEntry;
if (entry && entry.charset) {
return entry.charset;
}
if (mediaType.startsWith("text/")) {
return "UTF-8";
}
} catch {
// just swallow errors, returning undefined
}
return undefined;
}