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In this guide, we’ll show you how to transcribe multiple files simultaneously using the JavaScript SDK.

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Getting Started

Before we begin, make sure you have an AssemblyAI account and an API key. You can sign up for an account and get your API key from your dashboard. This guide will use AssemblyAI’s JavaScript SDK. If you haven’t already, install the SDK in your project by following these instructions.

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Step-by-Step Instructions

Set up your application folder structure by adding an audio folder which will house the files you would like to transcribe, a transcripts folder which will house your completed transcriptions, and a new .js file in the root of the project. Your file structure should look like this: 
BatchApp
├───audio
│   ├───audio-1.mp3
│   └───audio-2.mp3
├───transcripts
├───batch.js
In the batch.js file import the AssemblyAI package, as well as the node fs and node path packages. Create an AssemblyAI object with your API key: 
import { AssemblyAI } from "assemblyai";
import * as path from 'path';
import * as fs from 'fs';

const client = new AssemblyAI({
  apiKey: <Your API Key>,
});
Declare the variables audioFolder, files, filePathArr, and transcriptsFolder.
  • audioFolder will be the relative path to the folder containing your audio files.
  • files will read the files in the audio folder, and return them in an array.
  • filePathArr will join the file names with the audio folder name to create the relative path to each individual file.
  • transcriptsFolder will be the relative path to the folder containing your transcription files.
const audioFolder = './audio';
const files = await fs.promises.readdir(audioFolder);
const filePathArr = files.map(file => path.join(audioFolder, file));
const transcriptsFolder = './transcripts';
Next, we’ll create a promise that will submit the file path for transcription. Make sure to add the parameters for the models you would like to run. 
const getTranscript = (filePath) => new Promise((resolve, reject) => {
  client.transcripts.transcribe({
    audio: filePath,
    language_detection: true,
    speech_models: ["universal-3-pro", "universal-2"]
  })
  .then(result => resolve(result))
  .catch(error => reject(error));
});
Next, we will create an async function that will call the getTranscript function and write the transcription text from each audio file to an individual text file in the transcripts folder. 
const processFile = async (file) => {
  const getFileName = file.split('audio/'); //Separate the folder name and file name into substrings
  const fileName = getFileName[1]; //Grab the 2nd substring which is the file name
  const filePath = path.join(transcriptsFolder, `${fileName}.txt`); //Relative path for transcription text files.

  const transcript = await getTranscript(file); //Request the transcript
  const text = transcript.text; //Grab transcription text from the JSON response

  //Write the transcription text to a text file
  return new Promise((resolve, reject) => {
    fs.writeFile(filePath, text, err => {
      if (err) {
        reject(err);
        return;
      }

      resolve({
        ok: true,
        message: 'Text File created!'
      });
    });
  });
}
Next, we will create the run function. This function will:
  • Create an array of unresolved promises with each promise requesting a transcript.
  • Use Promise.all to iterate over the array of unresolved promises.
Then we’ll call the run function 
const run = async () => {
  const unresolvedPromises = filePathArr.map(processFile);
  await Promise.all(unresolvedPromises);
}

run()
Your final file will look like this: 
import { AssemblyAI } from "assemblyai";
import * as path from 'path';
import * as fs from 'fs';

const client = new AssemblyAI({
  apiKey: <Your API>,
});

const audioFolder = './audio';
const files = await fs.promises.readdir(audioFolder);
const filePathArr = files.map(file => path.join(audioFolder, file));
const transcriptsFolder = './transcripts'

const getTranscript = (filePath) => new Promise((resolve, reject) => {
  client.transcripts.transcribe({
    audio: filePath,
    language_detection: true,
    speech_models: ["universal-3-pro", "universal-2"],
  })
  .then(result => resolve(result))
  .catch(error => reject(error));
});

const processFile = async (file) => {
  const getFileName = file.split('audio/')
  const fileName = getFileName[1]
  const filePath = path.join(transcriptsFolder, `${fileName}.txt`);

  const transcript = await getTranscript(file);
  const text = transcript.text

  return new Promise((resolve, reject) => {
    fs.writeFile(filePath, text, err => {
      if (err) {
        reject(err);
        return;
      }

      resolve({
        ok: true,
        message: 'Text File created!'
      });
    });
  });
}

const run = async () => {
  const unresolvedPromises = filePathArr.map(processFile);
  await Promise.all(unresolvedPromises);
}

run()
If you have any questions, please feel free to reach out to our Support team at support@assemblyai.com.