dynamic shim load with callback

dynamicShim.js

function loadUserLeapAndRun(callback) {
  if (!window.UserLeap) {
    window.UserLeap = function(){U._queue.push(arguments)}
    let U = window.UserLeap;U.appId = 'xxxxxxxxx';U._queue = [];
    let a=document.createElement('script');
    a.async=1;a.src='https://cdn.userleap.com/shim.js?id='+U.appId;
    p=document.getElementsByTagName('script')[0];
    p.parentNode.insertBefore(a, p);
  }
}

if (some_app_state) {
  // loads the shim.js if not already loaded and executes the setUserId operation
  loadUserLeapAndRun();
  UserLeap('setUserId', '[INSERT (ANONYMIZED) USER ID]');
}