Why is it that script will run from using jquery's html but not from using innerHTML?

So I am a little confounded here. I do not understand why script executes when placed with jquery's .html() but not with innerHTML. I looked at the source code for jQuery's .html and it still seemed that innerHTML was being used. Can anyone explain this behavior?

I came across this during an ajax response. I was getting back html and a script tag with some javascript in it, and I usually use html, but for some reason had used innerHTML this time thinking there was no difference.

I understand that this might seem to be localized, so I made a jsFiddle with a timeout that behaves similar to an ajax response in order to highlight the issue.

jsFiddle demonstrating the behavior



As far as I can tell from a bit of breakpointin', jQuery will try to use innerHTML, but, failing that, it'll fall back to emptying the target element, and appending the new content via the DOM.

Update: see Felix Kling's comment below; basically, if the string content to be inserted contains script or style/link tags, jQuery won't use straight innerHTML

When that happens - and it does in your case - the content goes through a function called domManip which I don't claim to fully understand, but it does specifically look for and evaluate scripts.

So the short answer is: jQuery's not using innerHTML after all. Wish I could give you a better step-by-step of exactly what happens, but I don't know my way around jQuery's source well enough. I just set a breakpoint (at line 6074 in jQuery-1.9.1.js; the point where jQuery decides not to use innerHTML after all) and stepped around the source a little.


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