Toggle GeoJSON layer in leaflet sidebar

Question

How can I toggle the GeoJSON layers in my leaflet map as I would the L.marker layers?

https://jsfiddle.net/mawr35vj/

Please pardon me if this is a simple question, I'm still new to leaflet and have spent all day on this.

Here is the GeoJSON I would like toggled in the sidebar.

fetch('https://data.cityofnewyork.us/resource/ek5y-zcyf.geojson?$where=latitude is not null')
  .then(function (response) {
    // Read data as JSON
    return response.json();
  })
  .then(function (data2) {
    // Create the Leaflet layer for the data 
    var complaintLayer = L.geoJson(data2, {

      // We make the points circles instead of markers so we can style them
      pointToLayer: function (geoJsonPoint, latlng) {
        return L.circleMarker(latlng);
      },

      // Then we can style them as we would other features
      style: function (geoJsonFeature) {
        return {
          fillColor: '#0000ff',
          radius: 6,
          fillOpacity: 0.7,
          stroke: false
        };
      }
    });
  });

-I tried assigning it a "var"
-I tried adding "complaintLayer" in the overlays as I did with the L.marker
-And many other various things that I can't remember but is obviously not working...

Update:

I'm trying to load the GeoJSON and assign it a variable, but having difficulty. I'm looking at this and related threads: How can I assign the contents of a geojson file to a variable in Javascript?

I got it to work if I just copy and paste the GeoJSON into the script, but having difficulty if I want to load it from a local file or API.

Answer 1

You can put complaintLayer in an array for a marker control, but the variable must be in the right scope - from the code you've posted it looks like it's local to the function it's populated in, so it won't be visible outside.

Answer 2

Per peeebeee's suggestion, I fixed the issue by loading the data and putting them into a "promise."

you can see a working example below: https://jsfiddle.net/4x3sk1va/

Example of a promise below (taken from https://glitch.com/@ebrelsford)

// Fetch collisions data from our Glitch project
var collisionsFetch = fetch('https://cdn.glitch.com/03830164-a70e-47de-a9a1-ad757904d618%2Fpratt-collisions.geojson?1538625759015')
  .then(function (response) {
    // Read data as JSON
    return response.json();
  });

// Fetch lanes data from our Glitch project
var lanesFetch = fetch('https://cdn.glitch.com/fcedf615-7fef-4396-aa74-2e03fc324d71%2Fpratt-bike-routes.geojson?1538628711035')
  .then(function (response) {
    // Read data as JSON
    return response.json();
  });

// Once both have loaded, do some work with them
Promise.all([collisionsFetch, lanesFetch])
  .then(function (fetchedData) {
    console.log('Both datasets have loaded');

    // Unpack the data from the Promise
    var collisionsData = fetchedData[0];
    var laneData = fetchedData[1];

    // Add data in the order you want--first goes on the bottom
    L.geoJson(collisionsData).addTo(map);
    L.geoJson(laneData).addTo(map);
  });