JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <span>Get link #</span>
    <input id="num" type="number" value="1" />
    <input id="go" type="button" value="Go" />
    <p id="result">Result will be here</p>
</div>
<div id="links"></div>

CSS

a {
    font-size: 12px;
    display: block;
}

JavaScript

$(function() {
    var count = 500;
    var links = $('#links');
    for (var i = 1; i <= count; ++i) {
        links.append('<a href="#' + i + '">' + i + '</a>');
    }
    $('#go').click(function() {
        $('a').css('background', 'none');
        $('#result').text('');

        var selector = '#links a:nth-child(' + $('#num').val() + ')';
        $('#result').text(selector + ': ' + $(selector).length + ' element(s) found. Total: ' + $('#links a').length + ' elements');
        $(selector).css('background-color', 'red');
    });
});