Renames all files with certain file extension with increasing number on the end.

Rename.js

//requiring path and fs modules
const path = require("path");
const fs = require("fs");
//joining path of directory
const directoryPath = path.join(__dirname, "/");
//passsing directoryPath and callback function
fs.readdir(directoryPath, function (err, files) {
  //handling error
  if (err) {
    return console.log("Unable to scan directory: " + err);
  }
  //listing all files using forEach
  let a = 1;
  files.forEach(function (file) {
    // Do whatever you want to do with the file
    if (file.endsWith(".mp4")) {
      console.log(file);
      fs.rename(
        directoryPath + file,
        directoryPath + "Filename-" + a++ + ".mp4",
        function (err) {
          if (err) throw err;
        }
      );
    }
  });
});