How to read Blob as arraybuffer in react-native?

Question

I'm trying to convert Blob data into arraybuffer by using FileReader() but its not working giving me an error saying readAsArrayBuffer() is not implemented. so I search on web and found that this function is not implemented in react-native FileReader yet. react-native-Github

    var fileReader = new FileReader();
    fileReader.onload = function (evt) {
      var buffer = evt.target.result;
      var msgReader = new Utils.MsgToHmtl.MSGReader(buffer);
      var fileData = msgReader.getFileData();
      console.log(fileData);
    }

    fileReader.readAsArrayBuffer(file);

I also tried using react-native-fs but it's of no use since I wasn't able to find readAsArrayBuffer() function in that package. Is there any other package which will help me fixing this problem ?

get Blob from base64 String

const b64toBlob = (b64Data, contentType = '', sliceSize = 512) => {
    const byteCharacters = atob(b64Data);
    const byteArrays = [];

    for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
      const slice = byteCharacters.slice(offset, offset + sliceSize);

      const byteNumbers = new Array(slice.length);
      for (let i = 0; i < slice.length; i++) {
        byteNumbers[i] = slice.charCodeAt(i);
      }

      const byteArray = new Uint8Array(byteNumbers);
      byteArrays.push(byteArray);
    }

    const blob = new Blob(byteArrays, { type: contentType });
    return blob;
  }

Thank you for you're help :)