Inject ng app into running website via bookmarklet. (If security allows for it.)

bookmarklet.js

/**
 * Bookmarklet code, this will inject a script into what ever page your currently visiting when you click this favorite/bookmark link.
 * To install, just create a favorite/bookmark, then view the properties of is and change the name to something familiar.
 * Update the url to the next line, also you will need to modify the src attribute so that it points to the payload script you want to inject.
 */

javascript: (function () { var d = document; var h = d.getElementsByTagName('head')[0]; var s = d.createElement("script"); s.setAttribute("type", "text/javascript"); s.setAttribute("src", "http://www.somedomain.com/somescript.js"); h.appendChild(s); })();

payload.js

var html = document.getElementsByTagName("html")[0];
var head = document.getElementsByTagName("head")[0];
var body = document.getElementsByTagName("body")[0];
var element;

var template = `
<div style="z-index:10000; color:#fff; background-color:rgba(0,0,0,.5); position: fixed; width:300px; top: 10px; right: auto; left: 10px; bottom: 10px; padding: 10px; border-radius: 10px;">
  {{title}}
</div>
`

var fn = {
  init: () => {
    // If the site your injecting the script into doesn't already have angular, we'll add it.
    // Note: This doesn't check versions, you may want to add that if your having conflicts with angular > 1.7
    if (!window.angular)
      fn.ng();
    else
      fn.onLoad();
  },
  ng: () => {
    if (!window.angular) {

      var ngScript = document.createElement('script');
      ngScript.setAttribute("type", "text/javascript");
      ngScript.setAttribute("src", "https://ajax.googleapis.com/ajax/libs/angularjs/1.7.3/angular.js");

      head.appendChild(ngScript);

      // Wait a second for the stack to finish and for angular to get added before we continue.
      setTimeout(() => {
        // Make sure the page has a angular starting point.
        head.setAttribute("ng-app", "application");

        // Make sure there is a module present;
        angular.module('application', []);

        // Bootstrap angular into the app.
        angular.element(function () {
          angular.bootstrap(document, ['application']);
        });

        // Angular is ready to go
        fn.onLoad();
      }, 1000);
    }
  },
  onLoad: () => {
    // Create a new Element
    element = document.createElement('injected-element');

    // Add the template content into the element.
    element.innerHTML = template;

    //Inject the element as the first child of the body element
    body.prepend(element);

    // Execute the controller on the element.
    angular.element(document).injector().invoke(fn.controller);
  },
  controller: ['$rootScope', '$compile', function ($rootScope, $compile) {
    // Create a new isolated scope model to render with the view.
    var scope = $rootScope.$new(true);

    scope.title = "Hello World.";

    // Apply the scope to the view.
    $compile(element)(scope);

    // Force a digest to update the view.
    scope.$digest();
  }]
}

// Start it off.
fn.init();