Equivalent of Scala View in JavaScript

Question

In Scala, view allows preventing creating an entirely new collection. e.g. In Scala, what does "view" do?

Is there something similar in JavaScript? My use case:

x = inputValue.split(",").map(x => x.trim()).filter(f1).map(f2)

As you can see in the above code, 2 intermediate collections would be created. Is there some way in JavaScript to avoid creating the above intermediate collections?

Answer 1

Scala is a strict language similarily to Javascript. That means that if you create a list and use map, then Scala would eagerly create a new list:

//it creates List(2,3,4) and List(4,6,8) already when map is called
List(1,2,3).map(_ + 1).map(_ *2) 

You can make Scala collections lazy though by calling view:

val l = List(1,2,3).view.map(_ + 1).map(_ * 2) //nothing happens yet
l.take(2) //only 1 and 2 get processed 

Unfortunately, there is no built-in function in Javascript to make array behave lazily, but there is a library Lazy.js, which works similarly to Scala view:

Lazy([1,2,3]).map(x => x + 1).map(x => x * 2).take(2).toArray()

And according to docs:

What's important here is that no iteration takes place until you call each, and no intermediate arrays are created.