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std/front_matter/test.ts

Deno standard library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
import { MAP_FORMAT_TO_EXTRACTOR_RX } from "./_formats.ts";
type Format = "yaml" | "toml" | "json" | "unknown";
/** * Tests if a string has valid front matter. Supports YAML, TOML and JSON. * * @param str String to test. * @param formats A list of formats to test for. Defaults to all supported formats. * * ```ts * import { test } from "https://deno.land/std@$STD_VERSION/front_matter/mod.ts"; * import { assert } from "https://deno.land/std@$STD_VERSION/assert/assert.ts"; * * assert(test("---\ntitle: Three dashes marks the spot\n---\n")); * assert(test("---toml\ntitle = 'Three dashes followed by format marks the spot'\n---\n")); * assert(test("---json\n{\"title\": \"Three dashes followed by format marks the spot\"}\n---\n")); * * assert(!test("---json\n{\"title\": \"Three dashes followed by format marks the spot\"}\n---\n", ["yaml"])); * ``` */export function test( str: string, formats?: ("yaml" | "toml" | "json" | "unknown")[],): boolean { if (!formats) { formats = Object.keys(MAP_FORMAT_TO_EXTRACTOR_RX) as Format[]; }
for (const format of formats) { if (format === "unknown") { throw new TypeError("Unable to test for unknown front matter format"); }
const match = MAP_FORMAT_TO_EXTRACTOR_RX[format].exec(str); if (match?.index === 0) { return true; } }
return false;}