Note: Only JavaScript Boolean values (true or false) are supported when calling into Rust. If you want to pass truthy or falsy values to Rust, convert them to a boolean using Boolean(value) first.

If you are using TypeScript, you don't have to worry about this, as TypeScript will emit a compiler error if you try to pass a non-boolean value.

#![allow(unused_variables)]
fn main() {
use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn take_bool_by_value(x: bool) {}

#[wasm_bindgen]
pub fn return_bool() -> bool {
    true
}

#[wasm_bindgen]
pub fn take_option_bool(x: Option<bool>) {}

#[wasm_bindgen]
pub fn return_option_bool() -> Option<bool> {
    Some(false)
}

}

import {
  take_char_by_value,
  return_char,
  take_option_bool,
  return_option_bool,
} from './guide_supported_types_examples';

take_bool_by_value(true);

let b = return_bool();
console.log(typeof b); // "boolean"

take_option_bool(null);
take_option_bool(undefined);
take_option_bool(true);

let c = return_option_bool();
if (c == null) {
  // ...
} else {
  console.log(typeof c); // "boolean"
}