Pass Feature Attribute to Variable On Click - ESRI Leaflet

Question

I am building a leaflet map with feature layers that are hosted on ArcGIS online.

I would like to write a simple function so that when I click on a feature, the value of a particular column in the attribute table will be saved to a variable and logged to the console.

I have been able to get the value to appear in a pop-up, but not log to the console.

I have a feeling the solution has something to do with this, but I have limited experience with esri-leaflet so there is something I am missing:

https://esri.github.io/esri-leaflet/api-reference/tasks/identify-features.html

  var map = L.map('map').setView([40.1562,-75.057104], 9);
  L.esri.basemapLayer("Gray").addTo(map);

  var trails = L.esri.featureLayer({
    url: "https://services1.arcgis.com/Ps1YVQiv5JQLIFu2/arcgis/rest/services/CIRCUIT_TRAILS/FeatureServer/0",
    style: function () {
      return { color: "#70ca49", weight: 2 }; 
    }
  }).addTo(map);

  var popupTemplate = "<h3>{CIRCUIT_ID}</h3>";

  trails.bindPopup(function(e){
    return L.Util.template(popupTemplate, e.feature.properties)
    console.log(e.feature.properties.CIRCUIT_ID)

  });