testPromise.js

function analyze(i, callback) {
	setTimeout(() => {
		callback('result 123');
	}, Math.random()*10000);
	// long thinking time....
	// callback('result 123');
}

async function analyzeAsync(i) {
	return new Promise((resolve, reject) => {
		analyze(i, (result) => {
			console.log('ready', i);
			resolve({
				[i]: result
			});
		});
	});
}

async function sendDataAsync(param1, param2) {
	return new Promise((resolve, reject) => {
		sendData(param1, param2, (result) => {
			// process results
			resolve(result);
		});
	});
}

const data = [
	6, 1, 2, 3, 4, 5,
];

function callMeAfterAnalyze(data) {
	// use data
}
analyze(5, callMeAfterAnalyze);

analyze(5, (data) => {
	// use data
});

let total = {};

// takes 5 sec
(async () => {
	console.log('Slow...');
	console.time('slow');
	for (let i of data) {
		console.log(i);
		let result = await analyzeAsync(i);	// <- stop here
		// process results
		console.log('result', result);
		total[i] = result;
	}
	console.log('done', total);
	console.timeEnd('slow');

	console.log('Fast');
	// takes 1 sec
	console.time('fast');
	const setOfPromises = [];
	for (let i of data) {
		console.log(i);
		setOfPromises.push(analyzeAsync(i));
		// process results
	}
	console.log('loop done, ');
	const results = await Promise.all(setOfPromises);	// wait for all 5 requests at once
	console.log(results);
	console.timeEnd('fast');

})();