promises.ts

const fs = require('fs')
async function fileExists(path: string, flag: string): Promise<boolean> {
  return new Promise<boolean>((resolve, reject) => {
     fs.access(path, fs.F_OK, (err) => {
        if(err) {
          resolve(false); // no file exists
        }else{
         resolve(true);
        }
     });
  });
}