Find all CSS rules that apply to an element

Question

Many tools/APIs provide ways of selecting elements of specific classes or IDs. There\'s also possible to inspect the raw stylesheets loaded by the browser.

However,

Answer 1

EDIT: This answer is now deprecated and no longer works in Chrome 64+. Leaving for historical context. In fact that bug report links back to this question for alternative solutions to using this.

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Seems I managed to answer my own question after another hour of research.

It's as simple as this:

window.getMatchedCSSRules(document.getElementById("description"))

(Works in WebKit/Chrome, possibly others too)