JSFiddle - React, Tailwind, and code Playground

HTML

<p class = "thing1">This is thing1.</p>
<p class = "thing2">This is thing2.</p>
<p class = "thing1">This is also thing1.</p>
<p class = "thing2">This is also thing2.</p>

JavaScript

function highlightAllOnMouseover(className){
    $(className).mouseover(function() {
  $(className).css("opacity", 0.4); 
  $(className).css("opacity", 1);
}).mouseleave(function() { 
    $(className).css("opacity", 0.4);
});
}
highlightAllOnMouseover(".thing1");
highlightAllOnMouseover(".thing2");