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!
![JavaScript Promise API]()
While synchronous code is easier to follow and debug, async is generally better for performance and flexibility. Why "hold up the show" when you can trigger numerous requests at once and then handle them when each is ready? Promises are becoming a big part of the JavaScript world...
![Write Simple, Elegant and Maintainable Media Queries with Sass]()
I spent a few months experimenting with different approaches for writing simple, elegant and maintainable media queries with Sass. Each solution had something that I really liked, but I couldn't find one that covered everything I needed to do, so I ventured into creating my...
![Image Reflection with jQuery and MooTools]()
One subtle detail that can make a big difference on any web design is the use of image reflections. Using them too often can become obnoxious but using reflections on large, "masthead" images is a classy enhancement. Unfortunately creating image reflections within your...
![Sara Soueidan’s Favorite CodePen Demos]()
A few months ago, Chris Coyier shared his favorite CodePen demos right here on David's blog. A while back David asked me to share some of my favorite pens too, so here are some of the demos that have blown my mind in the past...
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