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denoland-deno/std/path/common.ts
2020-05-31 13:48:32 -04:00

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1.1 KiB
TypeScript

// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
/** This module is browser compatible. */
import { SEP } from "./separator.ts";
/** Determines the common path from a set of paths, using an optional separator,
* which defaults to the OS default separator.
*
* import { common } from "https://deno.land/std/path/mod.ts";
* const p = common([
* "./deno/std/path/mod.ts",
* "./deno/std/fs/mod.ts",
* ]);
* console.log(p); // "./deno/std/"
*
*/
export function common(paths: string[], sep = SEP): string {
const [first = "", ...remaining] = paths;
if (first === "" || remaining.length === 0) {
return first.substring(0, first.lastIndexOf(sep) + 1);
}
const parts = first.split(sep);
let endOfPrefix = parts.length;
for (const path of remaining) {
const compare = path.split(sep);
for (let i = 0; i < endOfPrefix; i++) {
if (compare[i] !== parts[i]) {
endOfPrefix = i;
}
}
if (endOfPrefix === 0) {
return "";
}
}
const prefix = parts.slice(0, endOfPrefix).join(sep);
return prefix.endsWith(sep) ? prefix : `${prefix}${sep}`;
}