SendScript

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

• Socket example
  • Module
  • Server
  • Client
• Reference
  • sendscript/api.mjs
  • sendscript/exec.mjs
• TypeScript
• Tests
• Formatting
• Changelog
• Dependencies
• License

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.

// ./example/math.mjs

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

Server

Here 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 api from '../api.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, square } = api(['add', 'square'], exec)

console.log(
  await square(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

100

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/api.mjs

The api module exports a function that takes two arguments.

1. The schema, which represents the values that are available.
2. 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 API for writing programs that can be sent to a server.

import api from './api.mjs'

const  { add, subtract } = api(
  ['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 API 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.

TypeScript

There is a good use-case to write an environment module in TypeScript.

1. Obviously the module would have the benefits that TypeScript offers when coding.
2. You can use tools like typedoc to generate docs from your types to share with consumers of your API.
3. You can use the types of the module to coerce your client to adopt the modules type.

# Create pretty docs for your module.
npx typedoc my-module.ts

Now we can use the my-module.ts file for the client API.

import type * as MyModule from './my-module'

import sendScriptApi from 'sendscript/api.mjs'

export default sendScriptApi([
  fnOne,
  fnTwo,
], /* perform websocket request */) as typeof MyModule

Note

Although type coercion on the client side can improve the development experience, it does not represent the actual type. Values are likely subject to serialization and deserialization, particularly when interfacing with JSON formats.

Tests

Tests with 100% code coverage.

npm t -- -R silent
npm t -- report text-summary

> [email protected] test
> tap -R silent


> [email protected] test
> tap report text-summary


=============================== Coverage summary ===============================
Statements   : 100% ( 110/110 )
Branches     : 100% ( 32/32 )
Functions    : 100% ( 10/10 )
Lines        : 100% ( 110/110 )
================================================================================

Formatting

Standard because no config.

npx standard

Changelog

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

npx auto-changelog -p

Dependencies

Check if packages are up to date on release.

npm outdated && echo 'No outdated packages found'

No outdated packages found

License

See the LICENSE.txt file for details.