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<html><head><script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script><script>$(document).ready(function(){ $("button").click(function(){ alert($(".hot").index($("#favorite"))); });});</script></head><body><p>Click the button to get the index of the element with id="favorite", relative to the jQuery selector (class="hot"):</p><button>Get index</button><ul> <li>Milk</li> <li class="hot">Tea</li> <li class="hot" id="favorite">Coffee</li></ul></body></html>