Initiates a multipart upload and returns an upload ID.

startMultiUpload.js

    /*
        Initiates a multipart upload and returns an upload ID.
        Upload id is used to upload the other parts of the stream
    */
    startMultiUpload(blob, filename) {
        var self = this;
        var audioBlob = blob;
        var params = {
            Bucket: self.bucketName,
            Key: filename,
            ContentType: 'audio/webm',
            ACL: 'private',
        };
        self.s3.createMultipartUpload(params, function(err, data) {
            if (err) {
                console.log(err, err.stack); // an error occurred
            } else {
                self.uploadId = data.UploadId
                self.incr = 1;
                self.continueMultiUpload(audioBlob, self.incr, self.uploadId, self.filename, self.bucketName);
            }
        });
    }