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.