Status: refused by design
var is not FunctionalScript. var a = 1 is valid JavaScript, and fjs compile refuses it by design: the demo below shows what it prints.
A var is a variable: it can be assigned again, it is visible before its declaration as undefined, and its scope is the whole function rather than its block. FunctionalScript binds a name with const, or with let as a variable of its block, declared before it is read (variables), so var is refused.
The row st.var of refused constructs registers the refusal, and constants gives its reason.
var a = 1;
export default a;
The demo on this page compiles sample.mjs, the module above, with this build's fjs compile, and shows the line it prints and the token it refuses. Below that it shows what JavaScript answers for the same module: 1.
Bind the name with const, as alternative.f.js does:
const a = 1;
export default a;
It answers 1.
Today fjs compile prints unexpected token at the refused token. The demo proposes what it should print instead: the reason at the same token, what JavaScript does there, and the allowed spelling, the line alternative.f.js writes, as help. The page compiles the alternative too, so the suggestion is one the compiler accepts.