javascript API 4.6 - Error not throwing up in mapView promise callback

Question

I notice that error that are thrown in the mapView constructor callback are not displayed in the browser console. For instance: var view = new MapView({ "container": "viewDiv", "map": map, "zoom": 7 }).when(function(view) { throw new Error("This error is not displayed in the browser console"); alert("This alert is not executed"); }, function(error) { console.error(error); });‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ This is really difficult to know where the code is breaking. Is there a solution for this?

YannCabon · Accepted Answer

Hi, This is a normal behavior. Here is an snippet using JS Promise that reproduce the same behavior: Promise.resolve().then( () => { throw new Error("throwing in the then() callback") }, (error) => { console.error("not catching the error", error); } ) .catch(error => { console.error("catching the error", error); }); ‍‍‍‍‍‍‍‍‍‍‍‍ You will see that the error callback won't react to what's happening in the success callback. As a good practice, I never use the error callback, only chain with .catch Promise.resolve().then( () => { throw new Error("throwing in the then() callback") } ) .catch(error => { console.error("catching the error", error); }) ‍‍‍‍‍‍‍‍‍ Your code snippet would look like: var view = new MapView({ "container": "viewDiv", "map": map, "zoom": 7 }); view.when(function(view) { throw new Error("This error is displayed in the browser console"); }) .catch(function(error) { console.error(error); }); ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ Also, make sure to first assign view to the MapView instance. // DON'T var view = new MapView().when(); // view is a promise // DO var view = new MapView(); // view is a MapView var promise = view.when();‍‍‍‍‍‍