differences between synchronous and asynchronous using Promise

asynchronous_Promise.js

const AWS = require('aws-sdk');

class StorageService {
	constructor() {
		this._S3 = new AWS.S3();
	}

	writeFile(file, meta) {
		const parameter = {
			Bucket: process.env.AWS_BUCKET_NAME, // Nama S3 bucket yang ingin digunakan
			Key: +new Date() + meta.filename, // Nama berkas yang akan disimpan
			Body: file._data, // Berkas (dalam bentuk Buffer) yang akan disimpan
			ContentType: meta.headers['content-type'], // MIME Type berkas yang akan disimpan
		};

    // GIVE ATTENTION TO THE CODES BELOW ========================================================================
		return new Promise((resolve, reject) => {
			this._S3.upload(parameter, (error, data) => {
				if(error) {
					return reject(error);
				}
	
				return resolve(data);
			});
		});
	}
}

module.exports = StorageService;

synchronous.js

const AWS = require('aws-sdk');

class StorageService {
	constructor() {
		this._S3 = new AWS.S3();
	}

	writeFile(file, meta) {
		const parameter = {
			Bucket: process.env.AWS_BUCKET_NAME, // Nama S3 bucket yang ingin digunakan
			Key: +new Date() + meta.filename, // Nama berkas yang akan disimpan
			Body: file._data, // Berkas (dalam bentuk Buffer) yang akan disimpan
			ContentType: meta.headers['content-type'], // MIME Type berkas yang akan disimpan
		};
    
    // GIVE ATTENTION TO THE CODES BELOW ========================================================================
		this._S3.upload(parameter, () => {
			if(error) {
				// upload error
				return;
			}

			// upload success
		});
	}
}

module.exports = StorageService;