What the suffix meaning (bg) with _bg.js and _bg.d.ts when we built into pkg folder?

[sombochea]

Summary

I so wonder about the built files in pkg folder. Because the files end with _bg.js and _bg.d.ts has defined different methods with parameter(s) when we return the method as String. But I don't know, why it's happened like that.

Additional Details

Note* I'm replaced the JavaScript to TypeScript! (not pkg files) and only file that have suffix _bg.d.ts that wrong export functions.

The function that have return String value

#[wasm_bindgen]
pub fn sample() -> String {
    "hello".into()
}

The function export in TypeScript

export function sample(a: number): void;

As that, I cannot return the value into output in JavaScript. I think, it can be cause by rust wasm or mis-configuration or something else.

Thank you!

[alexcrichton]

"bg" stands for "bindgen" here, and they're intended to be internal files generated by wasm-bindgen for your project.