websocket send with response

readme.md

websocket send with response

By default with WebSocket you only can send message.

0. Initialization

let ws = new WebSocket('ws://localhost:3000/ws')

ws.onopen = function(event) {
  console.log("on open")
}

ws.onclose = function(event) {
  console.log("on close")
}

ws.onmessage = function(event) {
  console.log("on message", event)
  let message = JSON.parse(event.data)
  // add here your logic
}

1. Default

function send(action, data) {
  ws.send(JSON.stringify({ action, data }))
  // no way to get response here
}

2. Impove
It enables you to send message and receive a response as a Promise.

// Map to associate message IDs with promises.
const promiseMap = new Map()

// Timeout duration for response.
const timeoutms = 10000 

// Improved function to send a message and wait for a response.
async function sendWithResponse(action, data) {
  return new Promise((resolve, reject) => {
    
    // Generate a unique ID for this message
    const id = Math.random().toString(36).substring(2, 15)
    // Send the message
    ws.send(JSON.stringify({ id, action, data }))
    
     // Set a timeout to reject the Promise and remove id from the map
    const timeoutId = setTimeout(() => {
      reject(new Error('timeout: no response'))
      promiseMap.delete(id)
    }, timeoutms)
    
    // Store the resolve function and timeoutId in the map
    promiseMap.set(id, { resolve, timeoutId })
  })
}

ws.onmessage = function(event) {
  console.log("on message", event)
  let message = JSON.parse(event.data)

  if (message.id && promiseMap.has(message.id)) {
    // Resolve the corresponding promise with the received message id.
    let { resolve, timeoutId } = promiseMap.get(message.id)
    clearTimeout(timeoutId)
    promiseMap.delete(message.id)
    resolve(message.data)
    return
  }
  // add here your logic
}

3. Usage

sendWithResponse("get_tree")
    .then(response => console.log(response))
    .catch(e => console.log("e", e))

sendWithResponse("get_file_content", {file: node.id})
    .then(response => console.log(response))
    .catch(e => console.log("e", e))

let response = await sendWithResponse("get_file_content", {file: node.id})