sendscript

SendScript

Write JS code that you can run on servers, browsers or other clients.

SendScript leaves it up to you to choose HTTP, web-sockets or any other method of communication between servers and clients that best fits your needs.

Socket example

For this example we'll use socket.io.

npm install --no-save socket.io socket.io-client

We use the --no-save option because it's only for demonstration purposes.

Module

We write a simple module that only has an add function

// ./example/math.mjs

export const add = (a, b) => a + b

Server

Here a simple module for running a socket.io server that runs SendScript programs.

// ./example/server.socket.io.mjs

import { Server } from 'socket.io'
import exec from '../exec.mjs'
import * as math from './math.mjs'

const server = new Server()
const port = process.env.PORT || 3000

server.on('connection', (socket) => {
  socket.on('message', async (program, callback) => {
    try {
      const result = await exec(math, program)
      callback(null, result) // Pass null as the first argument to indicate success
    } catch (error) {
      callback(error) // Pass the error to the callback
    }
  })
})

server.listen(port)
process.title = 'sendscript'

Client

Now for a client that sends a program to the server.

// ./example/client.socket.io.mjs

import socketClient from 'socket.io-client'
import dsl from '../dsl.mjs'

const port = process.env.PORT || 3000
const client = socketClient(`http://localhost:${port}`)

const exec = program => {
  return new Promise((resolve, reject) => {
    client.emit('message', program, (error, result) => {
      error
        ? reject(error)
        : resolve(result)
    })
  })
}

const { add } = dsl(['add'], exec)

console.log(
  await add(1, add(add(2, 3), 4))
)

process.exit(0)

Now we run this server and a client script.

# Run the server
node ./example/server.socket.io.mjs&

# Run the client example
node ./example/client.socket.io.mjs

pkill sendscript

10

Reference

SendScript is essentially a way to serialize a program to then send over the wire and execute it somewhere else.

We only have two modules. One that helps you write programs that can be sent over the wire and another for running that program.

sendscript/dsl.mjs

The dsl module exports a function that takes two arguments.

• The schema, which represents the values that are available.
• The function that will be called with the serializable version of the program.

It returns an object that contains functions which are defined in the schema. These functions are a JavaScript DSL for writing programs that can be sent to a server.

import dsl from './dsl.mjs'

const  { add, subtract } = dsl(
  ['add', 'subtract'],
  serializableProgram => sendSomewhereToBeExecuted(serializableProgram)
)

await add(1, 2) // => 3
await subtract(1, 2) // => -1
await add(1, subtract(2, 3)) // => 0

The add and subtract functions are thennable. The execute function is called as soon as await or .then is used.

Notice that you do not have to await the subtract call. You only need to await when you want to execute the program.

This DSL is composable and wrappable.

sendscript/exec.mjs

The exec function takes an environment object and any valid SendScript program.

import exec from './exec.mjs'

exec({
  add: (a, b) => a + b,
  subtract: (a, b) => a - b
}, ['add', 1, [subtract, 1, 2]])

The array you see here is the LISP that SendScript uses to represent programs.

You could use SendScript without knowing the details of how the LISP works. It is an implementation detail and might change over time.

Tests

Tests with 100% code coverage.

npx c8 --100 npm t -- -R classic

> sendscript@0.0.0 test
> tap *.test.mjs --no-cov -R classic

curry.test.mjs ........................................ 4/4
dsl.test.mjs .......................................... 5/5
exec.test.mjs ....................................... 15/15
total ............................................... 24/24

  24 passing (400.194ms)

  ok
-----------|---------|----------|---------|---------|-------------------
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-----------|---------|----------|---------|---------|-------------------
All files  |     100 |      100 |     100 |     100 |                   
 curry.mjs |     100 |      100 |     100 |     100 |                   
 debug.mjs |     100 |      100 |     100 |     100 |                   
 dsl.mjs   |     100 |      100 |     100 |     100 |                   
 error.mjs |     100 |      100 |     100 |     100 |                   
 exec.mjs  |     100 |      100 |     100 |     100 |                   
-----------|---------|----------|---------|---------|-------------------

Formatting

Standard because no config.

npx standard

Changelog

The changelog is generated using the useful auto-changelog project.

npx auto-changelog -p

License

See the LICENSE.txt file for details.

Changelog

v0.0.0

14 September 2023

• Initiate project 2a192b3