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test.ts
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test.ts
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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;
}