Specific web pages that should be light are a burden on the processors

I’ve been realizing for quite some time that some specific pages are a real burden for my browser to open. I hear the fans at full on speed and the processors seem to have a unusually high load when checking htop.

I’m not very familiar with web programming, but it seems to be something related to Javascript. It appears to happen independently of browser (I’ve tried Chromium, Chrome and Firefox) and it’s always the same pages. That happens even when I’m not doing anything else with my OS except viewing those pages.

Some examples of pages that spur that behavior are this page and Thesaurus.

Some relevant info:

I’m using an up-to-date Arch Linux with cinnamon.

Here’s a screeshot of htop as the issue was happening (at the time of the screenshot, browsing the internet was the only thing I was doing):