ts-promise.ts

const waitFor = (selector: string): Promise<NodeList> => {
  return new Promise(resolve => {
    const id = setInterval(() => {
      const elems = document.querySelectorAll(selector);
      if (elems.length >= 0) {
        clearInterval(id);
        resolve(elems);
      }
    }, 300);
  });
};

wait_for.js

function waitFor(selector) {
    return new Promise(resolve => {
        const id = setInterval(() => {
            const elems = document.querySelectorAll(selector);
            if (elems.length >= 0) {
                clearInterval(id);
                resolve(elems);
            }
        }, 200);
    });
}