const is replaced by var

[2beers]

// a.js
export const a = {
    a: "a"
};

// main.js
import {a} from "./a";
const v1 = a;
console.log(v1);


//out.js
// src/a.js
var a = {
  a: "a"
};

// src/main.js
var v1 = a;
console.log(v1);

I use the following command
esbuild src/main.js --bundle --format=esm --target=es2020 --outfile=out.js

const v1 = a; is replaced with var v1 = a;

Is there an option to keep const instead of var?

[remorses]

This is because in Safari declarations with const were much slower than var, is there any reason you want to keep const?

[evanw]

There are also some other reasons, which are described here: #598 (comment).

[2beers]

@remorses Not really. I assume only top level const/let are replaced with var?
I'm testing esbuild to see if I can replace rollup in a production project.

Maybe an option to enable/disable this behavior.

[evanw]

As mentioned above, this behavior is deliberate and is done for at least three reasons. It sounds like you don’t have a reason you need to keep const since you said “not really”? If so, I would like to close this issue and just keep the current behavior. I’m trying to keep the number of options that esbuild exposes low to avoid esbuild being unnecessarily complex to configure as a user and to avoid it being unnecessarily complex to develop and test for me. Each option has a cost and I’m not going to throw in more options unless there are strong reasons for them.

[2beers]

Sure. I understand. You can close this thread. I don't mind if it's using var on top level. It just looked weird when I saw it the first time, but I read your comment on the other thread and made more sense.