JSFiddle - React, Tailwind, and code Playground

by lbstr

HTML

<ul id="u">
    <li id="a">a</li>
    <li id="b">b</li>
    <li id="c">c</li>
    <li id="d">d</li>
</ul>

CSS

.red { color: red; }
.bold { font-weight: bold; text-decoration: underline; }

JavaScript

$.fn.neighbors = function(){
    var newCollection = this.prev().add(this.next());
    
    return this.pushStack(newCollection, "neighbors", "");
};

$('#b')
    .neighbors()
        .addClass('red')
        .end()
    .addClass('bold');