IFRAME contentWindow is null
I like clean code so I do what I can to avoid unwanted JavaScript global variables. I initially thought that keys(window) would give me window property leaks but that didn't work because browsers returned different results, so I moved on to using an IFRAME to compare default window property keys.
When I first tried this method, I got a lame error about an IFRAME element's contentWindow property being null. Ugh. It didn't take long to figure out why: you need to wait until the IFRAME has loaded to get the contentWindow:
var iframe = document.createElement('iframe');
iframe.onload = function() {
// contentWindow is set!
};
iframe.src = 'about:blank';
document.body.appendChild(iframe);
Of course you'll want to add the onload event before setting the src. If you use the load event to check for the contentWindow property, you'll be in business!
![CSS Animations Between Media Queries]()
CSS animations are right up there with sliced bread. CSS animations are efficient because they can be hardware accelerated, they require no JavaScript overhead, and they are composed of very little CSS code. Quite often we add CSS transforms to elements via CSS during...
![How to Create a Twitter Card]()
One of my favorite social APIs was the Open Graph API adopted by Facebook. Adding just a few META tags to each page allowed links to my article to be styled and presented the way I wanted them to, giving me a bit of control...
![Drag. Drop. Lock.]()
I've received dozens of emails about my Six Degrees of Kevin Bacon Using MooTools article. The MooTools in my article contained a lot of conditional code to require correct dropping per the game and many people requested that I simplify the process and just...
![Unicode CSS Classes]()
CSS class name structure and consistency is really important; some developers camelcase classnames, others use dashes, and others use underscores. One thing I've learned when toying around by HTML and CSS class names is that you can actually use unicode symbols and icons as classnames.
Don’t you need to append your iframe element to a DOM tree so that the browser fetches its target content ? I mean, I know that old IE will load scripts as you parse an “HTML string” but in modern browsers, I thought that the asset does not get loaded until you append the element to a document (and in my opinion this it what makes constructors such as
Image()so useful).Yes, good catch! Updated!
Unfortunately this does not appear to be 100% reliable in chrome (i’m currently using version 62.0.3202.94, but this appears to have been an issue for a while), as sometimes contentWindow can still be null when onload is triggered.
This solution worked for me! Thanks a lot!
Thank you, saved me hours!
Sharry