What should I do if IMG does not support onload labels? _ JavaScript

Webpage standards. IMG does not support onload labels. what should I do? webpage standards? IMG does not support onload labels. what should I do? I remember someone asked me before, but I didn't pay attention to this yet. now we finally have this problem. because the img tag does not have an onload event. therefore, the onload used by img in UBB code is used to handle large images for self-adaptation. this method cannot be used.
However, after testing, the body can still carry the onload event, so the solution is to process too large images after all the pages are loaded.

So I wrote a simple piece of code using JS.