Boa's boa_runtime crate contains an example runtime and basic runtime features and functionality for the boa_engine crate for runtime implementors.

Example: Adding Web API's Console Object

1. Add boa_runtime as a dependency to your project along with boa_engine.

use boa_engine::{js_string, property::Attribute, Context, Source};
use boa_runtime::Console;
use boa_runtime::console::DefaultLogger;

// Create the context.
let mut context = Context::default();

// Register the Console object to the context. The DefaultLogger simply
// write errors to STDERR and all other logs to STDOUT.
Console::register_with_logger(DefaultLogger, &mut context)
    .expect("the console object shouldn't exist yet");

// JavaScript source for parsing.
let js_code = "console.log('Hello World from a JS code string!')";

// Parse the source code
match context.eval(Source::from_bytes(js_code)) {
    Ok(res) => {
        println!(
            "{}",
            res.to_string(&mut context).unwrap().to_std_string_escaped()
        );
    }
    Err(e) => {
        // Pretty print the error
        eprintln!("Uncaught {e}");
        # panic!("An error occured in boa_runtime's js_code");
    }
};

Example: Add all supported Boa's Runtime Web API to your context

use boa_engine::{js_string, property::Attribute, Context, Source};

// Create the context.
let mut context = Context::default();

// Register all objects in the context. To conditionally register extensions,
// call `register()` directly on the extension.
boa_runtime::register(
    (
        // Register the default logger.
        boa_runtime::extensions::ConsoleExtension::default(),
        // A fetcher can be added if the `fetch` feature flag is enabled.
        // This fetcher uses the Reqwest blocking API to allow fetching using HTTP.
#       #[cfg(feature = "reqwest-blocking")]
        boa_runtime::extensions::FetchExtension(
            boa_runtime::fetch::BlockingReqwestFetcher::default()
        ),
    ),
    None,
    &mut context,
);

// JavaScript source for parsing.
let js_code = r#"
    fetch("https://google.com/")
        .then(response => response.text())
        .then(html => console.log(html))
"#;

// Parse the source code
match context.eval(Source::from_bytes(js_code)) {
    Ok(res) => {
        // The result is a promise, so we need to await it.
        res
            .as_promise()
            .expect("Should be a promise")
            .await_blocking(&mut context)
            .expect("Should resolve()");
        println!(
            "{}",
            res.to_string(&mut context).unwrap().to_std_string_escaped()
        );
    }
    Err(e) => {
        // Pretty print the error
        eprintln!("Uncaught {e}");
        # panic!("An error occured in boa_runtime's js_code");
    }
};