QuerySelector for Web Elements Inside iframe

Edit: New title. What I'm looking for is a document.querySelector for elements inside an iframe.

I've done quite a bit of Googling for an answer and finally I'm stumped.

I'm trying to query inside an iframe. I'm building string selectors to be used in Selenium and usually I just inspect the element with Firebug, and use document.querySelectorAll("theStringIBuid");

But it doesn't work with elements inside iframes. I've tried all of the below to get an element "radiobutton1" inside the "page-iframe" iframe.

var elem1 = ".page-iframe";
console.log(elem1);
var elem2 = ".radiobutton1";
console.log(elem2);
document.querySelectorAll(elem1+elem2+"");

document.querySelectorAll('.page-iframe').contentWindow.document.body.querySelectorAll('.radiobutton1')
document.getElementById('.page-iframe').contentWindow.document.body.innerHTML;

[].forEach.call( document.querySelectorAll('.page-iframe'), 
function  fn(elem){ 
console.log(elem.contentWindow.document.body.querySelectorAll('.radiobutton1')); });

var contentWindow = document.getElementById('.page-iframe').contentWindow 
var contentWindow = document.querySelectorAll('.page-iframe') 
var contentWindow = document.querySelectorAll('.page-iframe')[0].contentWindow

Thanks-

simple es6 adapted from h3manth:

document.querySelectorAll('iframe').forEach( item =>
    console.log(item.contentWindow.document.body.querySelectorAll('a'))
)

if the original page's url isn't at the same domain with the iframe content, the javascript will treat the iframe as a black box, meaning it will not see anything inside it.

You can do this:

document.querySelector("iframe").contentWindow.document.querySelector("button")

https://m.youtube.com/watch?v=-mNp3-UX9Qc

Here's a snippet for diving into same-origin frames (ie-compatible ES5):

function findInFramesRec(selector, doc) {
  var hit = doc.querySelector(selector);
  if (hit) return hit;
  var frames = Array.prototype.slice.call(doc.frames);
  for(var i = 0; (i < frames.length) &&   !hit   ; i++) {
    try {
      if (!frames[i] || !frames[i].document) continue;
      hit = findInFramesRec(selector, frames[i].document);
    } catch(e) {}
  }
  return hit;
}

This dives into both frameset frames and iframes alike. It may even survive (though not enter) cross origin frames.

You can simply use

document.querySelector("iframe").contentDocument.body.querySelector("#btn")

First query selector is to select the iframe. Then we can access ifram dom using content document and use the 2nd query selector to select the element inside iframe.