Adjust width and height of iframe to fit with content in it

Question

I need a solution for auto-adjusting the width and height of an iframe to barely fit its content. The point is that t

Answer 1

Context

I had to do this myself in a context of a web-extension. This web-extension injects some piece of UI into each page, and this UI lives inside an iframe. The content inside the iframe is dynamic, so I had to readjust the width and height of the iframe itself.

I use React but the concept applies to every library.

My solution (this assumes that you control both the page and the iframe)

Inside the iframe I changed body styles to have really big dimensions. This will allow the elements inside to lay out using all the necessary space. Making width and height 100% didn't work for me (I guess because the iframe has a default width = 300px and height = 150px)

/* something like this */
body {
  width: 99999px;
  height: 99999px;
}

Then I injected all the iframe UI inside a div and gave it some styles

#ui-root {
  display: 'inline-block';     
}

After rendering my app inside this #ui-root (in React I do this inside componentDidMount) I compute the dimensions of this div like and sync them to the parent page using window.postMessage:

let elRect = el.getBoundingClientRect()
window.parent.postMessage({
  type: 'resize-iframe',
  payload: {
    width: elRect.width,
    height: elRect.height
  }
}, '*')

In the parent frame I do something like this:

window.addEventListener('message', (ev) => {
  if(ev.data.type && ev.data.type === 'resize-iframe') {
    iframe.style.width = ev.data.payload.width + 'px'
    iframe.style.height = ev.data.payload.height + 'px'
  }
}, false)