promises-playground.ts

/**
 * Use with await to have synchrone delay
 */
const delay = (ms: number) => new Promise<void>(resolve => setTimeout(resolve, ms))

/**
 * Retry a promise a number of times if it failed
 */
async function retry<T>(promise: Promise<T>, maxRetries: number, delayBetweenRetriesMs: number = 0) {
	let res: T
	let i = 0

	while (i < maxRetries) {
		try {
			res = await promise
			break
		} catch (err) {
			i++
			await new Promise(resolve => setTimeout(resolve, delayBetweenRetriesMs))
		}
	}

	return res!
}
  
/**
 * Executes all promises one after the other and retrieve all results
 */
function sequenceAll<T>(tasks: Promise<T>[]): Promise<T[]> {
	return tasks.reduce(async (prevTask, task) => {
		const results: T[] = await prevTask
		const result = await task
		return results.concat(result)
	}, Promise.resolve([]))
}

/**
 * Executes all promises one after the other and retrieve only result of last promise
 */
function sequenceLast<T>(tasks: Promise<T>[]): Promise<T> {
	return tasks.reduce((prevTask, task) => prevTask.then(() => task), Promise.resolve(<unknown>null) as Promise<T>)
}