JSFiddle - React, Tailwind, and code Playground

HTML

<div id="left">
    <a href="http://fiddle.jshell.net/vaypssqw/show/"  >Страница 1</a>
    <a href="http://fiddle.jshell.net/vaypssqw/1/show/">Страница 2</a>
</div>
<div id="right"></div>

CSS

* {
    padding: 0;
    margin: 0;
}
html, body {
    width: 100%;
    height: 100%;
}
#left {
    border-right: 1px solid black;
    float: left;
    height: calc(100% - 6px);
    padding: 3px;
}
#left a {
    display: block;
}
#right {
    float: left;
}

JavaScript

var elements = document.querySelectorAll("#left a");
for(var n = 0; n < elements.length; n++)
{
    var element = elements[n];
    element.onclick = (function()
    {
        //console.log(element.href);
        var xmlhttp = new XMLHttpRequest()
        xmlhttp.open('GET', this.href, true);
        xmlhttp.onreadystatechange = function() {
            if (xmlhttp.readyState == 4) {
                if(xmlhttp.status == 200) {
                    document.querySelector("#right").innerHTML = xmlhttp.responseText;
                }
            }
        };
        xmlhttp.send(null);
        return false;
    }).bind(element);
};