ng-popups | Alert , confirm and prompt dialogs | Frontend Framework library

Serendipitously, I have been working on a different problem, and one of the byproducts of that problem may come in handy for you.

Your primary issue is the asynchronous nature of the click event. If you open up your map (the first jsfiddle in your comment), open your dev tools network tab, and start clicking around, you will see a new network request made for every click. That's how a lot of esri query functions work - they need to query the server and check the database for the value you want at the given latlng. If you tried to attach that same behavior to a mousemove event, you'll trigger a huge number of network requests and you'll overload the browser - bad news.

One solution of what you can do, and its a lot more work, is to read the pixel data under the cursor of the image returned from the esri image service. If you know the exact rgb value of the pixel under the cursor, and you know what value that rgb value corresponds to in the map legend, you can achieve your result.

And Here is the codesandbox source code. Don't be afraid to hit refresh, CSB is little wonky in the way it transpiles the modules.

What is happening here? Let's look step by step:

1. On map events like load, zoomend, moveend, a specialized function is fetching the same image that L.esri.dynamicMapLayer does, using something called EsriImageRequest, which is a class I wrote that reuses a lot of esri-leaflet's internal logic: