Discussion on: ES6 Arrow Functions Cheatsheet

Like a lots of things in JS, you can screw yourself if you're not careful with the flexible syntaxe.

ESlint (with airBnB rules) can help a lot with this. As you said, there's two (maybe three) ways to use arrow-functions. Here's the two syntaxes I enforce to myself.

1 Simple one-liner:

this.children.forEach(child => child.remove()); // Without implicit return
const translated = points.map(point => point.add(x, y)); // With implicit return

1.1 Object return:

const options = values.map(value => ({
  value: value,
  size: value.length,
}));

2 Multi-line operation:

object.data.forEach((data) => {
  test(data.value);
  test(data.size);
});

I personally feel in large projects we need to enforce the use of body braces and explicit returns, as that is the only syntax that will work consistently, regardless of the changes made to the function(adding a parameter, changing the return type, adding 1 more line).

I'm curious about your reasoning here and if you have any examples that could clear things up for me.

I don't see the syntax as being retired to project size.

Changing either the input or output of a function should be the same in both situations.

I feel like all optional symbols must be eradicated.
I'm just on the fence with returning someone else's undefined or even worse another return when you don't want a return.

as.forEach(x => map.set(a.name,a.value)) // Oh no, I am returning the map instance!
as.forEach(x => console.log(x)) // Oh no, I am returning `console.log`'s `undefined`

For the longest time, I would avoid that, adding a {}, especially if this is an otherwise available function.

const addToMap = x => { map.set(a.name,a.value) }
const log = x => { console.log(x) }

as.forEach(addToMap) // Ahh, bliss
as.forEach(log)

But then, on one cursed day, I once again stumbled upon ES6 tail call optimization spec. (Unlike most ES6, it is implemented ONLY in Safari & Mobile Safari, was REMOVED from Chrome, and is not in active development anywhere else.)

So, what is a tail call for that spec? Why, it's a function call the result of which is then returned, unconditionally. So you see my problem.
I have never had a night of good sleep since, and I am sure you can relate, since it would mean that functions like

const addToMap = x => map.set(a.name,a.value)
const log = x => console.log(x)

With the return value discarded as late as possible, are superior.