Connect iframes published on another domain (foreign sandbox)

local-connection npm GitHub last commit Travis

Get in contact for help from developer:

Gitter chat Get help on Codementor Website


This script is used to communicate and synchronise iframes placed in same parent window.

After you add this script to your project, it defines global LC object.

How it works:

Each and every window, those served in iFrames and need to connect to each other needs:

  • A unique key. A unique Key is important, so only and only companion windows(iframes) connects to each other.
  • A name belongs to themselves.
  • List of names of other frames, those having same key

If all required parameters given correctly, each connect method search for other windows those having correct key ,and then tries to match with given name

As soon as it finds any acceptable window, registers it as an element to LC object with it's name parameter.

From now on all connected windows can communicate with each other.


Name Type Required Description
key String YES Unique connection string. Set this value for all iframes that should communicate each other. Avoid using same key for all projects.
name String YES Give a different name to each banner.
frames String [Array] YES Define name of all other banners that will be connected to.
onConnect Function NO Define a function that will be called as soon as successfully connected to other iframes.
timeout Number NO Quit trying to connect after defined time in seconds. Default is 0 which means no timeout and keeps continuously try to connect.
onTimeout Function NO Define a function that will be called if timeout occurs. It will only be called if timeout is greater then 0.


connected : Boolean property that shows if connection established.


First thing ist first : link to LocalconnectionAPI (localconnection.min.js) script to each index.html. Minified version doesn't give any message to Browsers Console. During development it's also possible to use un-minified version localconnection.js to see logs, but It's not suggested to leave un-minified version in the final creative.

Place LocalconnectionAPI (localconnection.min.js) preferably just before the closing </head> tag, as follow:

<script src="localconnection.min.js"></script>

Then define options in each HTML page (which needs to connect with other)

    new LocalConnection({
        key: 'uniqueConnectionString',
        name: 'left',
        frames: ['top', 'right'],
        onConnect: function () {
                    From this point window of left and top will be available as
                    LC.left and LC.top
                    for example :

                LC.left.document.getElementsByTagName('body')[0].style.backgroundColor = 'pink';
        timeout: 0, // If you want to quit after a given amount of time set here as second 
        onTimeout: function () {
                    // If you set timeout property bigger than '0'
                    // this function will be called if no succes in connection


A working sample available in /test folder


-As soon as local connection established:

  • runs onConnect function. Therefore, stop or pause video, canvas or css animations and initialize these functions through onConnect method.

  • all defined frames are available to current LC object as child. For example banner left becomes child of LC in the frame top as LC.left as so on.

    Selenium Tests

Thanks to Browserstack for supporting opensource projects.

Browser Stack