Refers to the use of JavaScript to modify a WebPage as the user interacts with it.
This fell out of favour because relying on JavaScript for essential functionality is an accessibility hurdle and too likely to exclude a large proportion of visitors from viewing the page properly. This was particularly true in yesteryears when JavaScript and DOM implementations used to be extremly inconsistent between WebBrowsers, so that it was a huge headache to write scripts that would work for an acceptable minimum percentage of visitors.
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