mvm_call() error on multiple declarations of same variable across for loops

[Jerryxia32]

This reduced test case

console.log = vmImport(1);
function sayHello() {
	var arr = [1, 2, 3];
	for (var i = 0; i < 3; ++i) {
		console.log(arr[i]);
	}
	for (var i = 0; i < 3; ++i) {
		console.log(arr[i]);
	}
}
vmExport(1234, sayHello);

causes mvm_call() error with a return value of 12 when entering sayHello(), on tag 0.0.25.

My Javascript expertise is limited, but after some poking around I think it's the second var i = 0 in the second for loop that chokes Microvium. If I just change the second var i = 0 into i = 0, it works fine.

[coder-mike]

Thanks for the reporting this. I'll look into it.

In the meantime, can I suggest using let instead of var. In JS, var declarations are hoisted to the function level, so two var declarations with the same name in the same function are actually the same function-level var declaration, which can lead to subtle bugs in your code. Here's some more detail about the differences on Stack Overflow.

[coder-mike]

I've fixed this on main. The fix will go out with the next release. But as I say, I do recommend using let (or const) instead of var.