JSFiddle - React, Tailwind, and code Playground

HTML

<mysection>
    <form>
        <input name="myfield">
    </form>
</mysection>

JavaScript

Element.prototype.getElementsByName = function (arg) {
    var returnList = [];
    (function BuildReturn(startPoint) {
        for (var child in startPoint) {
            if (startPoint[child].nodeType != 1) continue;
            if (startPoint[child].getAttribute("name") == arg) returnList.push(startPoint[child]);
            if (startPoint[child].childNodes.length > 0) {
                BuildReturn(startPoint[child].childNodes);
            }
        }
    })(this.childNodes);
    return returnList;
};


var parent = document.getElementsByTagName('mysection')[0];
var myfield = parent.getElementsByName("myfield")[0];
console.log(myfield);