JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div">
    <a href="#" class="link">Link</a>
</div>
<div>
    <a href="#"class="link">Link</a>
</div>
<br /><br />
<div id="TestResults"></div>

JavaScript

var resultsLog = document.getElementById("TestResults");
var times = 10000;
var start = new Date().getTime();
var i;

resultsLog.innerHTML += "'#id' selector<br />";
for ( i = 0; i < times; i++ ) {
    document.getElementById("div");
}
resultsLog.innerHTML += "getElementById :: " + (new Date().getTime() - start) + "<br />";

start = new Date().getTime();
for ( i = 0; i < times; i++ ) {
    document.querySelectorAll("#div");
}
resultsLog.innerHTML += "querySelectorAll #id :: " + (new Date().getTime() - start) + "<br /><br />";

resultsLog.innerHTML += "'.class' selector<br />";
start = new Date().getTime();
for ( i = 0; i < times; i++ ) {
    document.getElementsByClassName("link");
}
resultsLog.innerHTML += "getElementsByClassName :: " + (new Date().getTime() - start) + "<br />";

start = new Date().getTime();
for ( i = 0; i < times; i++ ) {
    document.querySelectorAll(".link");
}
resultsLog.innerHTML += "querySelectorAll .class :: " + (new Date().getTime() - start) + "<br /><br />";

resultsLog.innerHTML += "'tag' selector<br />";
start = new Date().getTime();
for ( i = 0; i < times; i++ ) {
    document.getElementsByTagName("div");
}
resultsLog.innerHTML += "getElementsByTagName :: " + (new Date().getTime() - start) + "<br />";

start = new Date().getTime();
for ( i = 0; i < times; i++ ) {
    document.querySelectorAll("div");
}
resultsLog.innerHTML += "querySelectorAll tag :: " + (new Date().getTime() - start) + "<br /><br />";

resultsLog.innerHTML += "'tag.class' selector<br />";
start = new Date().getTime();
for ( i = 0; i < times; i++ ) {
    var tags = document.getElementsByTagName( "a" );
    var res = [];
    for ( var j = 0; j < tags.length; j++ ) {
        if ( tags[j].className.indexOf( "link" ) > -1 ) {
            res.push( tags[j] );
        }
    }
}
resultsLog.innerHTML += "getElementsByTagName/filter by class :: " + (new Date().getTime() - start) + "<br />";

start = new Date().getTime();
for ( i = 0; i < times; i++ ) {
   ...