SendScript

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

• Socket example
  • Module
  • Server
  • Client
• Async/Await
• TypeScript
• Tests
• Formatting
• Changelog
• Dependencies
• License
• Roadmap

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 link &&
  npm install --no-save \
    socket.io \
    socket.io-client \
    sendscript

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 Parse from 'sendscript/parse.mjs'
import * as math from './math.mjs'

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

server.on('connection', (socket) => {
  socket.on('message', async (program, callback) => {
    try {
      const result = parse(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 stringify from 'sendscript/stringify.mjs'
import module from 'sendscript/module.mjs'
import * as math from './math.mjs'
import assert from 'node:assert'

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

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

const { add, square } = module(math)

// The program to be sent over the wire
const program = square(add(1, add(add(2, 3), 4)))

const result = await send(program)

console.log('Result: ', result)

assert.equal(result, 100)

process.exit(0)

Now we run this server and a client script.

set -e

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

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

pkill sendscript

Result:  100

Async/Await

SendScript supports async/await seamlessly within a single request. This avoids the performance pitfalls of waterfall-style messaging, which can be especially slow on high-latency networks.

While it's possible to chain promises manually or use utility functions, native async/await support makes your code more readable, modern, and easier to reason about — aligning SendScript with today’s JavaScript best practices.

const userId = 'user-123'
const program = {
  unread: await fetchUnreadMessages(userId),
  emptyTrash: await emptyTrash(userId),
  archived: await archiveMessages(selectMessages({ old: true }))
}

const result = await send(program)

This operation is done in a single round-trip. The result is an object with the defined properties and returned values.

TypeScript

There is a good use-case to write a 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 module's type.

Let's say we have this module which we use on the server.

cat ./example/typescript/math.ts

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

We want to use this module on the client. We create a client version of that module and coerce the types to match those of the server.

cat ./example/typescript/math.client.ts

import module from 'sendscript/module.mjs'
import type * as mathTypes from './math.ts'

const math = module([
  'add',
  'square'
]) as typeof mathTypes

export default math

We now use the client version of this module.

cat ./example/typescript/client.ts

import stringify from 'sendscript/stringify.mjs'

async function send<T>(program: T): Promise<T>{
  return (await fetch('/api', {
    method: 'POST',
    body: stringify(program)
  })).json()
}

import math from './math.client.ts'

const { add, square } = math

send(square(add(1, 2)))

We'll also generate the docs for this module.

npm install --no-save \
  typedoc \
  typedoc-plugin-markdown

typedoc --plugin typedoc-plugin-markdown --out ./example/typescript/docs ./example/typescript/math.ts

You can see the docs here

[!NOTE] Although type coercion on the client side can improve the development experience, it does not represent the actual type. Values are subject to serialization and deserialization.

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% ( 245/245 )
Branches     : 100% ( 74/74 )
Functions    : 100% ( 18/18 )
Lines        : 100% ( 245/245 )
================================================================================

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.

Roadmap

• [ ] Support for simple lambdas to compose functions more easily.