JSFiddle - React, Tailwind, and code Playground

HTML

<button id="btn1">Change all "someElements"</button>
<button id="btn2">Change only divs with "someElement"-class</button>

<ul>
    <li class="id1 someElement">item 1</li>
    <li class="id2">item 1</li>
    <li class="id3">item 1</li>
    <li class="id4">item 1</li>
<ul>
    
<div class="someElement">Div</div>

JavaScript

$.fn.someFunction = function(){
    this.each(function(){
        // only handle "someElement"
        if (false == $(this).hasClass("someElement")) {
            return; // do nothing
        }
        
        $(this).append(" modified");
        
        return $(this); // support chaining
    });    
};

// execute function on all "someElements"
$('#btn1').click(function() {
        $('.someElement').someFunction();
});

// in fact you could also use this function on any element
$('#btn2').click(function() {
    $('div').someFunction(); // would only alter div.someElement
});