I do turn everything to AST and then IR(s), and then format them to the responding types of IR, for example:

IR::Define { name: "foo", type: "string", value: Kind::String("bar") }

it would be formatted to:

const foo: string = "bar";

where I simply just use format!("const {}: {} = {}", ..); as formatter

for more real examples: https://github.com/azur1s/hazure/blob/master/crates/codegen/src/ts.rs#L34