JSFiddle - React, Tailwind, and code Playground

JavaScript

var mapping = {
    //allowDom: false,
    //dom: 'no dom'
}

dom = (function() {
    switch (false) {
      case mapping.allowDom == null:
        return mapping.allowDom;
      case mapping.dom == null:
        return mapping.dom;
      default:
        return true;
    }
  })();

console.log("dom is " + dom);