How can I run a command once fs is done writing to a file?

Here is the code in question:

        const scriptFiles = fs.readdirSync(scriptsPath)
            .filter(file => file.endsWith(".sql"));

        for (const file of scriptFiles) {

            var data = fs.readFileSync(`${scriptsPath}/${file}`, 'utf8');
            fs.appendFile(`${scriptsPath}/Hotfix.sql`, data.toString() + "\n", (err) => {
                if (err) throw new Error(err)
                console.log('Appending ' + file + '...')
            })

            process.stdout.cursorTo(0);
        }

        console.log(`start ${scriptsPath}/Hotfix.sql`)
        exec(`start ${scriptsPath}/Hotfix.sql`)

The problem that I'm running into is that it is attempting to open/start scriptsPath/Hotfix.sql before anything has been appended to the file. For example, here is the output from the console.log()s I've added to the script:

start scriptsPath/Hotfix.sql
Appending file1.sql...    
Appending file2.sql...

is there a way I can have the script wait until the for loop has completed before attempting to execute the command?

Replace the appendFile() asynchronous method with the appendFileSync() synchronous method so that code waits until the loop has completed.

const scriptFiles = fs.readdirSync(scriptsPath)
  .filter(file => file.endsWith(".sql"));

for (const file of scriptFiles) {

  var data = fs.readFileSync(`${scriptsPath}/${file}`, 'utf8');
  fs.appendFileSync(`${scriptsPath}/Hotfix.sql`, data.toString() + "\n");

  process.stdout.cursorTo(0);
}

console.log(`start ${scriptsPath}/Hotfix.sql`)
exec(`start ${scriptsPath}/Hotfix.sql`)