completeMultiUpload.js

   /*
        Completes a multipart upload by assembling previously uploaded parts.
    */
    completeMultiUpload() {
        var self = this;
        var outputTag = [];
        /*
            here we are constructing the Etag data in the required format.
        */
        self.etag.forEach((data, index) => {
            const obj = {
                ETag: data,
                PartNumber: ++index
            };
            outputTag.push(obj);
        });

        var params = {
            Bucket: self.bucketName, // required 
            Key: self.filename, // required 
            UploadId: self.uploadId, // required 
            MultipartUpload: {
                Parts: outputTag
            }
        };

        self.s3.completeMultipartUpload(params, function(err, data) {
            if (err) {
                console.log(err, err.stack)
            } // an error occurred
            else {
                // initialize variable back to normal
                self.etag = [], self.recordedChunks = [];
                self.uploadId = "";
                self.booleanStop = false;
                self.disableAllButton();
                self.removeLoader();
                alert("we have successfully saved the questionaire..");
            }
        });
    }