JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="out"></pre>

JavaScript

const obj = {className: 'test', id: 'item_42'};

const str = `<ul class="{{ className }}" id="{{ id }}"></ul>`;

const myReplaceFunc = (full, key) => obj[key];

out.textContent = str.replace(/{{\s*(\S+?)\s*}}/g, myReplaceFunc);