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http://hop.inria.fr Hop.js: a multitier JavaScript

Hop.js (aka Hop) is:

  • A multitier JavaScript:
    • a single code runs on the client and the server.
  • A compliant JavaScript implementation:
    • EcmaScript 5.1 compliant;
    • EcmaScript 6 features (modules, async/await, proxy objects, ...);
    • Nodejs compatibility.
  • An extended JavaScript:
    • builtin HTML: native HTML syntax support and multitier dom.
    • server-side web workers.
    • websockets.
  • Two implementations:
    1. A Nodejs embedding (i.e., Hop can be installed inside Nodejs via an NPM package).
    2. A builtin multi-threaded web server.

Note

Hop also supports the Scheme programming language. When using the nativer Hop.js version (as opposed to the Nodejs hostsed version), JavaScript and Scheme are fully interoperable and applications can mix both languages. This page mostly describes the JavaScript layer. The Scheme layer is described in a dedicated programming manual.

Hop programs execute in the context of a builtin web server. They define services, which are super JavaScript functions that get automatically invoked when HTTP requests are received. As service associates an URL to a JavaScript and enables calls by the means of HTTP requests:

// hello.hop.mjs
import { Hop } from "@hop/hop";

const hop = new Hop({ports: {http: 8888}});

function hello(o) {
  return "hello world";
}

const Hello = hop.Service(hello);
hop.listen().then(() => console.log(`${Hello()} ready...);

To run this program put this code in the file hello.hop.mjs, compile it

$ hopc.mjs hello.hop.mjs -o hello.mjs

and execute it:

$ nodejs hello.mjs

You can now browse http://localhost:8888/hello.

Hop extends JavaScript with the geniune HTML. if we want to modify our service to make it return an HTML document, we can use:

function hello() {
  return <html><div>hello world</div></html>;
}

Hop is multitier. That is client-side codes are also implemented in Hop. The ~{ mark switches from server-side context to client-side context:

function hello() {
  return <html><div onclick=~{alert("world")}>hello</div></html>;
}

Hop client-side code and server-side can also be mixed using the \${ mark:

service hello({ name: who }) {
  return <html><div onclick=~{ lert("Hi " + ${who} + "!")}>hello</div></html>;
}

By default Hop.js only accepts to serve authenticated requests. Users must be declared when creating the server. The following declare a user named hopjs whose password is inria and that is allowed to execute any Hop.js service, the declaration services: "\*", and download any file readable from the server process, the declaration directories: "\*":

import { Hop } from "@hop/hop";

const users = [ {
      "name": "hopjs",
      "password": "ENCRYPTED-PASSWORD",
      services: "*",
      directories: "*"
   }, { 
      name: "anonymous",
      services: ["wizard"],
      directories: hop.loadPath
   } ];
   
const hop = new Hop({ports: {http: 8888}, users});

You are now ready to execute Hop.js programs! Many more additional examples can be found in the source development tree.

[main page] | [hello world] | [language] | [license]