JavaScript Ninja – How To Tell If You’re Running Code From Within A SandBox’ed IFRAME

How to know if you are running from within an iframe,
which has set to be sandbox’ed – without allowing scripts execution?

essentially you try and fail (an error will still be presented in the console)
to modify a close-related variable, which requires an injection/execute of
a script in the local-scope (self).

the following code, will give you an explicit
yes/no answer, for the script-sandbox state you are currently running from.

It is useful if you’re running a JavaScript code, that
is originated from a Chrome-extension,
with "all_frames": true, set in the content_scripts.

function is_sandboxed(){
  var is_sandbox;

  self.is_sandbox = true;

  var script      = self.document.createElement("script");
  //script.onload, .onerror, .ontimeout will not work..
  //wrapping the next line with try/catch will not work either, and still render an error... but you can't error handle it since error handling is in itself a forbidden usage.

  is_sandbox = true === self.is_sandbox; //true, explicit.
  self.is_sandbox = undefined;           //cleanup.

  return is_sandbox;

if you want a test environment, you can use this plain
example in

<!doctype html>
<html itemscope="" itemtype="" dir="ltr" lang="en-US" language="English" charset="UTF-8" encoding="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"/>
  <meta http-equiv="Content-Type"    content="text/html;charset=UTF-8"/>
  <meta name="fragment"              content="!"/>
  <meta name="viewport"              content="height=device-height,initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0,user-scalable=no,width=device-width,minimal-ui"/>
<iframe src="about:blank" sandbox=""></iframe>

than right click the result (on the right), click “view source”,
and switch to the newly-opened tab,
remove the “view-source:” prefix of the URL, and open up chrome’s console,
select the scope, for the “about:blank” iframe, and try running the code above.

The code uses the self, to explicitly work with current iframe.