A simple javascript to rename the .srt filename to it's movie file. Note: currently support .mkv file only & both mkv and srt should be in same directory.

syncMovieAndSrt.js

'use strict';
const fs = require('fs');
const path = process.argv[2];
console.log('\n\nRunning script...');

if (!path) {
  console.log('Please provide a path');
  process.exit();
}


function startProcessing() {
  console.log(`Finding directories inside ${path}`);
  var AllFilesAndDir = fs.readdirSync(path);
  var directories = AllFilesAndDir.filter((name) => name.indexOf('.') < 0)
  if (!directories || !directories.length) return console.log('No directories found inside given path');
  console.log(`${directories.length} directories found -> `, directories.join(', '), '\n\n');

  directories.forEach((dir) => {
    let files = fs.readdirSync(path + dir);
    let movieFile = files.find((item) => item.match(/.mkv$/));
    let srtFile = files.find((item) => item.match(/.srt$/));
    if (movieFile && srtFile) renameFile(path, dir, srtFile, movieFile);
    else console.log(`No srt or .mkv file found inside ${dir}`);
  })
}


function renameFile(path, dir, srtFileName, movieFileName) {
  let oldFileName = srtFileName;
  let newFileName = movieFileName.slice(0, movieFileName.indexOf('.mkv')) + '.srt';

  console.log(`srt and mkv files found inside   ${dir}`);
  console.log(`  Renaming '${oldFileName}' to '${newFileName}'`);
  fs.renameSync(path + dir + '/' + oldFileName, path + dir + '/' + newFileName);
};



startProcessing();