text: Q:
  
  leaflet error: this.callInitHooks is not a function error?
  
  I'm using leaflet v1.5.1.
  The error from Chrome is:
  
  leaflet.js:5 Uncaught TypeError: this.callInitHooks is not a function
        at Object.i [as Marker] (leaflet.js:5)
        at map1Rose2.php:77
  
  Below is the minimal code that will reproduce the issue in Chrome. I do NOT see an issue with the function. The error appears at the first 'var' (line 77) in the .
  I've prodded and poked at this thing to exhaustion does anyone have an idea?
  <!DOCTYPE html>
  
  <html lang="en">
  <head>
  
      <title>NCM Map of Station Locations</title>
  
      <meta charset="utf-8" />
      <meta name="viewport" content="width=device-width, initial-scale=1.0">
  
      <link rel="shortcut icon" type="image/x-icon" href="images/favicon-32x32.png" >
  
      <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> 
  
      <!-- ******************************** Load LEAFLET from CDN *********************************** -->
     <link rel="stylesheet" href="https://unpkg.com/leaflet@1.5.1/dist/leaflet.css"
    integrity="sha512-xwE/Az9zrjBIphAcBb3F6JVqxf46+CDLwfLMHloNu6KEQCAWi6HcDUbeOfBIptF7tcCzusKFjFw2yuvEpDL9wQ=="
    crossorigin=""/>
    <script src="https://unpkg.com/leaflet@1.5.1/dist/leaflet.js"
    integrity="sha512-GffPMF3RvMeYyc1LWMHtK8EbPv0iNZ8/oTtHPx9/cc2ILxQ+u905qIwdpULaqDkyBKgOaB57QTMg7ztg8Jm2Og=="
    crossorigin=""></script>
       <!-- ********************************* End Load LEAFLET **************************************** -->
  
       <!-- ******************************** Load ESRI LEAFLET from CDN ******************************* -->
       <script src="https://unpkg.com/esri-leaflet@2.2.4/dist/esri-leaflet.js"
      integrity="sha512-tyPum7h2h36X52O2gz+Pe8z/3l+Y9S1yEUscbVs5r5aEY5dFmP1WWRY/WLLElnFHa+k1JBQZSCDGwEAnm2IxAQ=="
      crossorigin=""></script>
  
      <!-- Load Esri Leaflet Geocoder from CDN -->
      <link rel="stylesheet" href="https://unpkg.com/esri-leaflet-geocoder@2.2.14/dist/esri-leaflet-geocoder.css"
      integrity="sha512-v5YmWLm8KqAAmg5808pETiccEohtt8rPVMGQ1jA6jqkWVydV5Cuz3nJ9fQ7ittSxvuqsvI9RSGfVoKPaAJZ/AQ=="
      crossorigin="">
      <script src="https://unpkg.com/esri-leaflet-geocoder@2.2.14/dist/esri-leaflet-geocoder.js"
      integrity="sha512-uK5jVwR81KVTGe8KpJa1QIN4n60TsSV8+DPbL5wWlYQvb0/nYNgSOg9dZG6ViQhwx/gaMszuWllTemL+K+IXjg=="
      crossorigin=""></script>   
  
      <!-- ******************************** End ESRI LEAFLET ***************************************** -->
  
       <!-- ******************************** Added Functionality *************************************** -->
      <link rel="stylesheet" href="css/leaflet_numbered_markers.css" />
      <link rel="stylesheet" href="css/L.Grid.css" />   
      <link rel="stylesheet" href="css/L.Control.MousePosition.css" />
      <link rel="stylesheet" href="css/control.w3w.css" />
  
      <link rel="stylesheet" href="https://ppete2.github.io/Leaflet.PolylineMeasure/Leaflet.PolylineMeasure.css" />
      <link rel="stylesheet" type="text/css" href="css/maps.css">
  
      <link rel="stylesheet" type="text/css" href="css/leaflet/leaflet.contextmenu.min.css">
  
      <script src="js/leaflet_numbered_markers.js"></script>
      <script src="js/L.Grid.js"></script>   <!-- https://github.com/jieter/Leaflet.Grid -->
      <script src="js/L.Control.MousePosition.js"></script>  <!-- https://github.com/ardhi/Leaflet.MousePosition -->
  
      <script src="https://cdnjs.cloudflare.com/ajax/libs/OverlappingMarkerSpiderfier-Leaflet/0.2.6/oms.min.js"></script>
      <script src="js/control.w3w.js"></script>
      <script src="https://ppete2.github.io/Leaflet.PolylineMeasure/Leaflet.PolylineMeasure.js"></script>
  
      <script src="js/leaflet/leaflet.contextmenu.min.js"></script>
  
      <script src="https://unpkg.com/leaflet.maidenhead@1.0.0/src/maidenhead.js"></script>
  
      <script src="https://cdn.jsdelivr.net/npm/leaflet-geometryutil@0.9.1/src/leaflet.geometryutil.min.js"></script>
  
      <!-- https://github.com/Turfjs/turf -->
      <script src="https://cdn.jsdelivr.net/npm/@turf/turf@5/turf.min.js"></script>
  
      <style>
      </style>
  
  </head>
  <body>
  
  <!-- the map div holds the map -->
  <div id="map"></div>
  
  <script>
      var WA0TJT = L.Marker(new L.LatLng(39.202911,-94.602887),{
          contextmenu: true,
          contextmenuWidth: 140,
          contextmenuItems: [{ text: 'Click here to add mileage circles', callback: circleKoords}],               
          icon: new L.NumberedDivIcon({number: '1' }),
          title:"marker_1" }).addTo(fg).bindPopup("1<br><b>ID: #0013</b><br>WA0TJT<br>Keith Kaiser<br>Platte  Co., MO Dist: A<br>39.202911, -94.602887<br>EM29QE").openPopup();
  
      var KA0OTL = L.Marker(new L.LatLng(39.233702,-94.635126),{
          contextmenu: true,
          contextmenuWidth: 140,
          contextmenuItems: [{ text: 'Click here to add mileage circles', callback: circleKoords}],               
          icon: new L.NumberedGreenDivIcon({number: '2' }),
          title:"marker_2" }).addTo(fg).bindPopup("2<br><b>ID: #0025</b><br>KA0OTL<br>Jeff Libby<br>Platte  Co., MO Dist: A<br>39.233702, -94.635126<br>EM29qf").openPopup();
  
  /*              
  var map = L.map('map', {
      center: [39.73, -104.99],
      zoom: 10,
      layers: [base, pois]
  });
  */
  
  var fg = new L.featureGroup();
  
  function circleKoords(e) { };
  
  </script>
  
  </body>
  </html>
  
  A:
  
  You have to call new L.Marker() or L.marker() 
  To fix your second error (in the comments) you have to define first your featureGroup and then create the markers.
  var fg = new L.featureGroup();
  
  var WA0TJT = L.Marker(new L.LatLng(39.202911,-94.602887),{
          contextmenu: true,
          contextmenuWidth: 140,
          contextmenuItems: [{ text: 'Click here to add mileage circles', callback: circleKoords}],               
          icon: new L.NumberedDivIcon({number: '1' }),
          title:"marker_1" }).addTo(fg).bindPopup("1<br><b>ID: #0013</b><br>WA0TJT<br>Keith Kaiser<br>Platte  Co., MO Dist: A<br>39.202911, -94.602887<br>EM29QE").openPopup();
  
  also you will nothing see on the map, because you are not added your featuregroup to the map. And you need a map instance.
  var map = L.map('map', {
  ...
  });
  fg.addTo(map);
  
  