Node lookup executable in $PATH

which.js

#!/usr/bin/env node

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

function getExecutablePath(name) {
  const paths = process.env.PATH.split(':');

  return paths
    .map((dir) => Path.join(dir, name))
    .find((path) => isExecutable(path));
}

function isExecutable(path) {
  try {
    const stats = FS.statSync(path);
    if (!stats.isFile()) return false;
    FS.accessSync(path, FS.constants.F_OK | FS.constants.X_OK);

    return true;
  } catch (err) {
    if (['ENOENT', 'EACCES'].includes(err.code)) {
      return false;
    }

    throw err;
  }
}

const names = process.argv.slice(2);

names.forEach((name) => {
  const path = getExecutablePath(name);

  if (typeof path == 'undefined') {
    console.log(`${name} not found`);
  } else {
    console.log(path);
  }
});

Will probably create an async version later.