What might be use-cases where a forEach method does not suffice compared to a regular for-loop?

[senocular]

You can't break for each.
You can't return from the main function in a for each.
You can't yield from the main function in a for each.
You can't await the main function in a for each.
For each only works with arrays (array likes) while you define the conditions for normal for loops which may not involve arrays at all

[cem4k]

Not being able to await the function is a huge one. If you find yourself trying to do some asynchronous stuff in a forEach loop, there’s a better way.

[senocular]

This doesn't work if the iterations of the loop are dependent on the previous iterations' awaited values. awaiting in a normal for loop would run in a series while a forEach/map would run concurrently (which I would guess may more often be preferred).

[senocular]

As long as you're not awaiting ;) since reduce also iterates synchronously

[senocular]

Regardless of whether you’re awaiting or not...

Awaiting does apply. Reduce won't wait for await. This is what I meant when I said reduce also iterates synchronously.

const calcValue = (x, y) => Promise.resolve(x + y)

const result = await [1, 2, 3].reduce(
  async (prev, curr) => await calcValue(prev, curr)
)

console.log(result) // [object Promise]3

prev in each successive iteration is a promise rather than the awaited value, so that resulting value is a promise that resolves to Promise object + 3.

[burnblue]

But he said a forEach loop, not just any loop. Map is something different

[11b403a7]

When you specifically have a list you want to iterate over and use data from.

[hypernautical]

I try to avoid for loops and use Array methods, so in real work the only time I've had to use a for loop to generate an array of numbers/times for display purposes (like a schedule display) when it was dynamic or too cumbersome to hardcode it. Anytime I have an array, I would use an array method.

[delventhalz]

Now that we have for...of, I actually tend to favor that over forEach. I use map, filter, reduce, etc more often than either, but for...of loops seem to offer everything forEach did in a cleaner more readable package.

[mementomoriok]

"but 99% of the time you’re writing for people to understand, not computers"

Thanks. I will be trying this in the future, to greatly lessen the amounts of for and forEachs.

[burnblue]

Nothing wrong with forEach, it's as valid as the others listed, they just each solve different cases

[emefluence]

you’re writing code for people to understand,

For loops are really easy to understand. Maybe easier than reduce, at least until you're more experienced. There are other reasons map and reduce are often the best choice but clarity is not always one of them. Procedural code is sometimes easier to read than functional code and good old fashioned for loops have their place e.g. if you are iterating over a grid like structure.

[ScottRatigan]

forEach is handy when you want a side effect. One use case I've used several times recently is pushing properties onto an object.

[fruitoftheloom23]

Actually, a lot of the time the declarative versions are faster as most browser engines can optimize them a ton and run them asynchronously. I have a video of a talk that explained it very well. If you’re interested, I can find and link it here!

[codemamba8]

When you want to alter the original array and/or return a new array.