I have been going through some code and converting all the jQuery to vanilla JS. Below is some code I converted successfully (commented out is the jQuery). I was having some trouble appending it to the head until I added [0] at the end.I know square brackets are used when accessing an array, but I'm not exactly sure why they were needed in this instance. Could someone explain?
var head = document.getElementsByTagName('head')[0];
    var linkScript = document.createElement('link');
    linkScript.type = 'text/css';
    linkScript.rel = 'stylesheet';
    linkScript.href = purecommHostFiles + 'style.css';
    head.appendChild(linkScript);
    // $('<link>')
    //  .appendTo('head')
    //  .attr({
    //      type: 'text/css',
    //      rel: 'stylesheet',
    //      href: purecommHostFiles + 'style.css'
    //  });
 
    