Does let create two blocks in for loop?

Question

function A() {
  let local = "local";

  for (let i = 0; i < 4; i++) {
    var var_variable = "var_variable";
    const k = 10;
    {
      var block = "block";
    }
    function inside() {
      console.log("yo");
    }
    inside();
  }
}

A();

I know let and const are block scoped.

If you see from the image, let variable i has an own block and the for loop block which contain const scoped to that block and var which is scoped to that execution context.

My question is does let get copied into the for loop block in each iteration and destroyed?

I think the specs should answer your question : https://www.ecma-international.org/ecma-262/6.0/#sec-for-statement-runtime-semantics-labelledevaluation — Seblor, Jan 10 '21 at 10:33

score -1 · Answer 1 · answered Jan 10 '21 at 10:28

let basically allows that variable be used within that scope, as you mention you're familiar with. To answer your question, it's valid within the for loop until the end of the scope of that block of code. It's not "copied in" every time, the variable i is made at the call of the for() loop, then cleared / lost when the for loop ends.

See https://www.w3schools.com/js/js_let.asp for more info on scopes

Does let create two blocks in for loop?

1 Answers1