On: How necessary are var, let, and const?

[bmeck]

const can be used to denote that a reference to the variable is being passed around and should not change for the lifetime of a scope.

    function f() {
      const queue = [];
      consumer(queue);
      return queue;
    }

It could be important to note that removing const has benign effect, but that it is there to ensure a programmer does not change the value of queue between `consumer(queue)` and `return queue`. Easily reasoned about, but extra safeguards from introducing bugs is always nice.

[financequoll → bmeck]

I'm not sure I quite understand your point - while it's true that the variable called queue won't be reassigned, const would still allow elements and properties to be added to queue.

[bmeck → financequoll]

const is not about immutability in JS.

[financequoll → bmeck]

I know that - but the previous comment made it sound as though it did mean immutability.

[EugeneOZ → bmeck]

Ironically enough, but your example shows where const is shouldn't be used as guarantee of immutability: https://t.co/JIQozGe7Md

[agumonkey → EugeneOZ]

Isn't that a typical "corner case" in the understanding of dynamic languages bindings ? I think I've seen the same question pop about python. The array binding is constant, its content isn't.

[EugeneOZ → agumonkey]

if value of constant can be changed, it's not constant. In my understanding. And by Wikipedia: http://en.wikipedia.org/wiki/Constant_(computer_programming)

[agumonkey → EugeneOZ]

That's typical computer lingo / semantic issue. the `const` mean shallow/pointer constant, not deep/structurally constant.

[bmeck → EugeneOZ]

const is not about immutability in JS.

[digi_owl → bmeck]

I guess you can say that they are there to allow the compiler to check the intent of the programmer.