Why is var not deprecated?

Question

Lately after ES6 released, many sources suggested that I use \"const\" and \"let\" instead of \"var\", and that I should stop using \"var\" in my JavaScript.

What I

Answer 1

I believe sometimes you need to redeclare a variable to write less code.

One example is this function that generates a unique id:

function makeUniqueId(takenIds) {
  do {
    var id = Number.parseInt(Math.random() * 10);
  } while (takenIds.includes(id))
}

Which may be invoked like that

makeUniqueId([1,2,3,4,5,6,7])

Here I declare id variable simply inside do block and it get's "hoisted" to the function scope. That would cause an error if I used let, because while block wouldn't see the variable from the do block. Of course I could declate let before do..while, but that would create the same function scoped variable with extra line of code.

Another example is when you copypaste code to devtools console and every time variables get redeclared.

One more example. What if you want to keep your variable declarations close to their usages but still treat them as function globals? If you use let in this fashion, you'll get rather confusing expirience in dev tools (all those Block, Block scopes).

But var 'keeps' them together in one 'Local' list: