Using forEach to chain methods

Question

One of the advantages I've heard for the use of forEach vs a for/of on an iterable is that you can chain methods together.

As a basic example of the two I have:

let arr = [1,2,3];
arr.forEach((elem, idx) => {
    console.log(elem);
})
for (let elem of arr) {
    console.log(elem);
};

What would be an example of chaining together multiple forEach's?

Well you can't chain together multiple `forEach`s since `Array.prototype.forEach` returns undefined no matter what. — Samathingamajig, Mar 22 '22 at 19:36

score 2 · Accepted Answer · answered Mar 22 '22 at 19:36

forEach returns undefined. You can't call a method on undefined.

The chaining you might have heard about is when forEach is at the end of some processing which returns an array, like after array methods like map,reduce etc:

let arr = [1,2,3];

arr.map(x => x*2).forEach((elem, idx) => {
    console.log(elem);
})

score 1 · Answer 2 · answered Mar 22 '22 at 19:36

1

forEach always returns undefined. forEach is not chain-able like map, reduce or filter.

answered Mar 22 '22 at 19:36

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Using forEach to chain methods

2 Answers2