importScript.js

function importScript(src) {
    return new Promise((resolve, reject) => {
      const script = document.createElement("script");

      script.async = 1;
      script.type = "text/javascript";
      script.src = src;
      script.onerror = reject;
      script.onload = () => {
        document.body.removeChild(script);
        resolve();
      };

      document.body.appendChild(script);
    });
  }