Why should forEach be preferred over regular iterators?

Question

I was reading airbnb javascript guide. There is a particular statement, that says:

Don’t use iterators. Prefer JavaScript’s higher-order functions ins

Answer 1

forEach iterations cannot be delayed by await. This means you cannot use forEach to pipeline, let's say, web requests to a server.

Also forEach is not present on async Iterables.

Consider the following cases:

1

let delayed = (value)=>new Promise(resolve => setTimeout(() => resolve(value), 2000));


(async ()=>{
    for(el of ['d','e','f'])console.log(await delayed(el))
    
})();


(async()=>{
    
    ['a','b','c'].forEach(async (el)=>console.log(await delayed(el)))
   
})();

Result:

d
a
b
c
e
f

The elements of [d,e,f] array are printed every two seconds.

The elements of [a,b,c] array are printed all together after two seconds.

2

let delayed = (value)=>new Promise(resolve => setTimeout(() => resolve(value), 2000));

async function* toDelayedIterable(array) {
    for(a of array)yield (await delayed(a))    
}


for await(el of toDelayedIterable(['d','e','f']))console.log(el)

toDelayedIterable(['a', 'b', 'c']).forEach(async(el)=>console.log(await el));

Result:

d
e
f
Uncaught TypeError: toDelayedIterable(...).forEach is not a function

The elements of [d,e,f] array are printed every two seconds.

Error when trying to access forEach on the asyncIterator of [a,b,c] array.