const is not read-only... or is that a configuration?

[brocoppler]

Starting with the following script:

const a = 2;
var ret = false;
try {
	a = 3;
} catch (e) {
	if (e instanceof TypeError) {
		ret = true;
	}
}

ret;

Babel transpiles to:

"use strict";

function _readOnlyError(name) { throw new TypeError("\"" + name + "\" is read-only"); }

var a = 2;
var ret = false;

try {
  3, _readOnlyError("a");
} catch (e) {
  if (e instanceof TypeError) {
    ret = true;
  }
}

ret;

See the _readOnlyError function added

While swc transforms to:

"use strict";
function _instanceof(left, right) {
    if (right != null && typeof Symbol !== "undefined" && right[Symbol.hasInstance]) {
        return right[Symbol.hasInstance](left);
    } else {
        return left instanceof right;
    }
}
var a = 2;
var ret = false;
try {
    a = 3;
} catch (e) {
    if (_instanceof(e, TypeError)) {
        ret = true;
    }
}
ret;

Which does not make the const read-only. Is there a configuration for this?

[kdy1]

No, it seems like swc is doing something wrong.

[brocoppler]

Okay, thanks. I'll open an issue and see if I can find out what's going on