Discussion on: Demystifying Array.prototype.flat

[Brad]

Does anyone know why the arr.flat() doesn't automatically use Infinity as the default value? Is it a performance thing or something?

Also, could you ever shoot yourself in the foot with this call, or does it protect me from my own shenanigans?

[Zak Henry]

could you ever shoot yourself in the foot with this call, or does it protect me from my own shenanigans?

Yep you can shoot yourself in the foot - if for some reason your array contains circular references .flat(Infinity) will cause a stack overflow.

demo:

a = [1,2,3]

b = [4,5,6]

a.push(b)

b.push(a)

a.flat(Infinity) 

// VM185:9 Uncaught RangeError: Maximum call stack size exceeded
//    at Array.flat (<anonymous>)
//    at <anonymous>:9:3

[Laurie]

Depends what the shenanigans are! 🙃

And to be honest, I’m surprised so many people expected it to be infinity by default?

[rhymes]

It make sense, flat(N) means I have to know exactly how many levels of nesting there are. We're lazy, Infinity should have been the default :P