wasm-eval v0.1.1

Description

This crate can evaluate expressions like ("{} + {} * {}", ["1","2","3"]). It was developed to eval JavaScript-code of the client in a safe context.

The crate is based on the Rust eval-crate and its supported operators are:

! != "" '' () [] . , > < >= <= == + - * / % && || n..m.

See for supported operators.

Requirements

Your web-server must support the application/wasm Mime-Type.

Example for Jetty:

//add new mime-type mapping
ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
MimeTypes mt = context.getMimeTypes();
mt.addMimeMapping("wasm", "application/wasm");

Usage

Import the wasm-module into your app (e.g. import in ember via ember-auto-import):

(async () => {
    // Importing wasm module
    const { eval_syn, schedule_eval } = await import('wasm-eval')
    const values = ["1", "2," "3"];
    const expr = "{} + {} * {}";

    //eval_syn returns the value directly
    console.log(eval_syn(expr, values)); // 1 + 2 * 3 = 7

    /**
     * returns a promise (non-blocking) 
     * Useful for long expressions
     */
    schedule_eval(expr, values).then(res => {
        if(res) {
            console.log(res); // 7
        } else { // null is returned on parse error
            console.log("Could not parse expression");
        }
    });
})();