javascript demo of using async/await keyword ( with Promise resolve setTimeout )

test_async_await.js

/**
 * @author Thitipong Samranvanich 
 * @since  2561-09-05
 * @param {*} ms 
 * @desc  
 * 			Demo ofy async / await keyword  
 * 
 */

// ========================================================================================================
// REF : sleep function from 
//		 URL https://stackoverflow.com/questions/951021/what-is-the-javascript-version-of-sleep  
// REF : settimeout is not direc return Promise object 
//		 URL https://stackoverflow.com/questions/33289726/combination-of-async-function-await-settimeout
// REF : async/await keyword  
//       https://medium.com/pnpsolution/%E0%B8%A7%E0%B8%B4%E0%B8%98%E0%B8%B5%E0%B8%81%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%8A%E0%B9%89%E0%B8%87%E0%B8%B2%E0%B8%99-async-await-%E0%B9%83%E0%B8%99-node-js-b11d3f51689e
//		 https://medium.freecodecamp.org/avoiding-the-async-await-hell-c77a0fb71c4c
//		 https://blog.panjmp.com/async-await-%E0%B9%80%E0%B8%A3%E0%B8%B2%E0%B8%A1%E0%B8%B2%E0%B8%A3%E0%B8%B9%E0%B9%89%E0%B8%88%E0%B8%B1%E0%B8%81-syntax-%E0%B8%97%E0%B8%B5%E0%B9%88%E0%B8%88%E0%B8%B0%E0%B8%A1%E0%B8%B2%E0%B9%80%E0%B8%9B%E0%B8%A5%E0%B8%B5%E0%B9%88%E0%B8%A2%E0%B8%99%E0%B9%82%E0%B8%A5%E0%B8%81%E0%B8%82%E0%B8%AD%E0%B8%87-javascript-%E0%B8%81%E0%B8%B1%E0%B8%99-3f02091eca05 
// ========================================================================================================
function sleep2(ms) {
	return new Promise(resolve => setTimeout(resolve, ms));
}

// same as sleep2 , but implicit 
function sleep(ms){
	return new Promise(
		function(resolve){
			setTimeout(resolve,ms)
		}
	)
}

// function random(n){
// 	return  Math.floor(Math.random() * n ); 
// }

async function longRun (fn_name,delay_ms ){
	let rnd100 = delay_ms  
	console.log( fn_name + ":JOB /" +  rnd100 + "ms ...  START ")
	await sleep(rnd100 )
 	console.log( fn_name + ":JOB /" +  rnd100 + "ms ...  finished ")
}

//==============================================
async function run_sync(){	
	  console.log ("=====  run SYNC.START  ====")
	  await longRun("A1",500)
	  await longRun("A2",50)
	  await longRun("A3",100)
	  console.log ("=====  run SYNC.END  ====")
}

//==============================================
async function run_async(){	
	  console.log ("=====  run ASYNC.START  ====")
	  longRun("A1",500)
	  longRun("A2",50)
	  longRun("A3",100)
	  console.log ("=====  run ASYNC.END  ====")
}

async function main(){
	console.log ("=====  SYNC / ASYNC  function , with sleep()  ====")
	console.log("\n")
	await run_sync()
	console.log("\n");
	run_async()
	var fn = (x) => { return x*2  } 
	var n20 = fn(10)
	console.log(" === END OF proc main === ")
}

main()

// END OF SCRIPT 

z_console_result.txt

$ node test_async.js
=====  SYNC / ASYNC  function , with sleep()  ====


=====  run SYNC.START  ====
A1:JOB /500ms ...  START
A1:JOB /500ms ...  finished
A2:JOB /50ms ...  START
A2:JOB /50ms ...  finished
A3:JOB /100ms ...  START
A3:JOB /100ms ...  finished
=====  run SYNC.END  ====


=====  run ASYNC.START  ====
A1:JOB /500ms ...  START
A2:JOB /50ms ...  START
A3:JOB /100ms ...  START
=====  run ASYNC.END  ====
 === END OF proc main ===
A2:JOB /50ms ...  finished
A3:JOB /100ms ...  finished
A1:JOB /500ms ...  finished