Find parent folder with file in node js

Question

I want to be able to find target.json by passing a path to startingPoint.txt to a function in Node JS, given the following folder structure:

- root
 - sub1
  - sub2
    startingPoint.txt
 target.json

I've found a node package for it called find-up, but this is the kind of thing that probably takes no more than 6 lines of code.

export function findUp(start: Path, target: string): Path | undefined {
  // this code here
}

const pathToTarget = findUp("root/sub1/sub2/startingPoint.txt", "target.json"/);
console.log(pathToTarget); // "root/target.json"

Greg Ward · Accepted Answer · 2021-02-11 06:00:23Z

Old question I know, but I've just had to implement something similar and spent ages trying to find a good solution.

So, for future explorers, heres my solution using path and fs modules.

const PATH = require('path');
const FS   = require('fs');

function findInPathAncestry(path, target) {

    let current_directory_path = PATH.normalize(path).split(PATH.sep);
    let result = false;

    while(current_directory_path.length && !result) {

        let current_path = current_directory_path.join(PATH.sep)+PATH.sep+target;

        if(FS.existsSync(current_path)) {

             result = current_path;
        }

        current_directory_path.pop();
    }

    return result;
}

usage example:

// example file structure:
// C:\
// | - path\
// | --- to\
// | ----- start\
// | ------- at\
// | ----- findme.txt


let start_location = "C:\path\to\start\at";
let target_file    = "findme.txt";

console.log(findInPathAncestry(start_location, target_file));

// expected output:
// C:\path\to\findme.txt
// or false if file doesn't exist in path

the use of PATH.normalize and PATH.sep allows this to work in windows and unix environments

https://nodejs.org/api/path.html#path_path_sep

Seph Reed · Accepted Answer · 2019-12-09 23:49:46Z

Here's what I have for now:

import { join, dirname } from 'path';
import { existsSync } from 'fs';

export let MAX_BACK_STEPS = 50;

export function findUp(start: string, target: string, boundary?: {
  path: string,
  inclusive: boolean,
}): string | null {
  let currentDir = dirname(start);
  let lastTry = false;
  let backSteps = 0;
  while (backSteps++) {
    if (backSteps >= MAX_BACK_STEPS) {
      console.error("Too many back steps");
      return null;
    }

    if (boundary && boundary.path.includes(currentDir)) {
      if (boundary.inclusive && lastTry === false) {
        lastTry = true;
      } else {
        return null;
      }
    }

    const targetTestPath = join(currentDir, target);
    if (existsSync(targetTestPath)) {
      return targetTestPath;
    }

    currentDir = join(currentDir, "../");
  }
}

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