Pass value to iframe from a window

javascript

cross-origin-communication

iframe-communication

postmessage

byAnton Shumikhin·Aug 29, 2024

Use postMessage to transmit data to an iframe:

Parent to iframe:

// Knock Knock, iframe are you there? Let's be buddies and talk!
document.getElementById('myIframe').contentWindow.postMessage('Your Value', '*');

Iframe receives:

// Keep calm and listening for messages
window.addEventListener('message', (event) => {
    // Secure Check: am I talking to the right buddy?
    if (event.origin === 'http://your-parent-origin.com') {
        console.log(event.data); // 'Your Value'
    }
}, false);

Remember, '*' allows any origin or replace with your specific reliable origin.

Cracking the code: Exploring data-transfer methods

Method 1: URL parameters

Passing data through URL parameters is the most common, basically like tossing a note to your friend. However, remember to sanitize these prior to use, and remember, the longer the note, the more possibility of it tearing off.

Method 2: Cross-origin communication

Working with iframes from different origins? Cross-origins can sound scary like a crime movie but postMessage is your undercover agent. Make sure to double-check the sender’s badge (i.e., event.origin) matches the trusted source.

Method 3: The iframe onload timing

Why hurry? Let the iframe load completely and then chit-chat, iframe.onload is the relaxed approach to establish a conversation. Now, this is not the 'Fast & Furious'!

Method 4: Handling received data

Once you collect some facts (aka data), it's logical to store them in relevant boxes (aka objects) for easy access. Say goodbye to cluttered information!

Method 5: Reaching the right mailboxes

You don't want to send a message to the wrong mailbox, right? Use window.frames['frameName'] to make your message land in the right mailbox aka iframe.

Advanced communication methods for iframes

When sandboxing is a good thing

Applying the sandbox attribute on your iframes can be like a well contained, super secure play area where iframe actions are under control. But remember, excessive control can sometimes result in a boring play-time!

CORS: The messenger between cross-origin iframes

Dealing with iframes across different origins? CORS is your passport. Set the passport stamp (Access-Control-Allow-Origin headers) correctly, and you're good to go globe-trotting... I mean... origin-trotting.

Data validation: It's quality, not quantity

Do not accept any messages uncritically. Always, and I repeat, always validate and sanitize your incoming data.

Don't overburden the messenger

Keep in mind, postMessage is your friend, not a load bearer. Don't overload with large chunks of data. Keep data transfers minimal and efficient like "lightsaber" communication.