Example of using BroadcastChannel to communicate with pages in the same domain

screenshot.md

window-talk.js

/**
 * Instructions (updated to use BroadcastChannel)
 *
 * - open the JS console and run this code
 * - if nothing happens, enable popups in the browser URL bar
 * - wait for windows to load
 * - click on any of the open windows to see them all change color
 * - hit Esc to close all windows
 */

/**
 * Setup broadcast channel on each window
 */
function init (win) {
  // utility functions
  const getColor = () => {
    return '#' + Math.floor(Math.random() * Math.pow(255, 3)).toString(16)
  }

  const setColor = (color) => {
    win.document.body.style.background = color
  }

  // set up channel
  const bc = new BroadcastChannel('colors')

  // receive events
  bc.addEventListener('message', (event) => {
    setColor(event.data)
  })

  // send events
  win.document.addEventListener('mousedown', (event) => {
    const color = getColor()
    setColor(color)
    bc.postMessage(color)
  })
}

/**
 * Setup window layout
 */
function setup (cx, cy) {
  // screen bounds
  const s = {
    w: screen.availWidth,
    h: screen.availHeight,
    l: screen.availLeft,
    t: screen.availTop,
  }

  // window layout
  const w = Math.floor(s.w / cx)
  const h = Math.floor(s.h / cy)

  // create windows
  const windows = []
  for (let y = 0; y < cy; y++) {
    for (let x = 0; x < cx; x++) {
      // create window
      const win = window.open('', `window_${x}_${y}`, [
        `width=${w}`,
        `height=${h - 60}`,
        `left=${s.l + (w * x)}`,
        `top=${s.t + (h * y)}`,
        `scrollbars=no,resizable=no,status=no,location=no,toolbar=no,menubar=no`,
      ].join(','))

      // implement functionality on load
      win.addEventListener('load', () => {
        // setup broadcast channel
        init(win)

        // set window text
        win.document.body.innerHTML = '<pre style="padding: .5rem; line-height: 1.7">Click: Change color<br>Esc: Close windows</pre>'
  
        // setup window closing
        windows.push(win)
        win.document.addEventListener('keydown', (event) => {
          if (event.key.toLowerCase().includes('esc')) {
            windows.forEach(win => {
              win.close()
            })
          }
        })
      })    
    }  
  }
}

// run code
setup(5, 3)