main.rs

#![feature(link_args)]

#[link_args = "-s EXPORTED_FUNCTIONS=['_hello_world']"]
extern {}

extern crate semver;

use semver::Version;
use semver::VersionReq;

#[no_mangle]
pub fn hello_world() -> bool {
    // let r = VersionReq::parse(">= 1.0.0").unwrap();
    // let v = Version::parse("1.0.0").unwrap();

    true
}

fn main() {
    /* Intentionally left blank */
}

wrapper.js

var Module = require("./main.js");

var hello_world = Module.cwrap('hello_world', 'boolean', []);

var result = hello_world();
console.log("result: ", result);