ArcGIS Online and CORS Error

[EmilioPetrangeli]

Hi there, 

I'm going crazy with a CORS error in my ReactJS app (cra app).

I followed the tutorial to use @arcgis/core in ReactJS, as well as copying the assets inside the public folder, and everything seems to be working fine from that prospective.
@arcgis/core - npm (npmjs.com)

I created a Developer Account in ArcGIS online, and an API Key as specified here: Display a map | Overview | ArcGIS API for JavaScript 4.24 | ArcGIS Developers

My app is a copy/paste of the one shown as example in the developer portal:

esriConfig.apiKey = 'xxxx';
esriConfig.assetsPath = '/assets';

const map = new Map({
	// Basemap layer
	basemap: 'arcgis-topographic'
});

const view = new MapView({
	container: mapDiv.current,
	map: map,
	center: [-118.805, 34.027],
	zoom: 13, // scale: 72223.819286
	constraints: {
		snapToZoom: false
	}
});

Now when I run my application locally I keep getting the following CORS errors:

Access to fetch at 'https://ibasemaps-api.arcgis.com/arcgis/rest/services/Elevation/World_Hillshade/MapServer?f=json&tok...}' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

I fully understand how CORS works in a normal web/server applicartion, but here I cannot understand how I cann allowe my localhost (or the full app url once deployed), from my  ArcGIS online Developer Dashboard.

In my ArcGIS online Organization settings I left the "Allow origins" list empty, this shoudl allow all.
But even if I try to add https://localhost, this is not accepted by the system.

Am I missing anything?

[AndyGup]

Hi @EmilioPetrangeli  can you try again using the sample here: https://github.com/Esri/jsapi-resources/tree/master/esm-samples/jsapi-create-react-app? I'm not sure which tutorial you are using, for example you don't need to configure the assetsPath for most installs, the default pattern is to the use CDN-hosted assets as described here: https://developers.arcgis.com/javascript/latest/es-modules/#working-with-assets.

[EmilioPetrangeli · Accepted solution]

Hi All, 

I solved my problem disabling Azure App Insights JS library for my project (actually I just disabled arcgis domain).
The library intercepts all the requests and inject some custom headers to trak them, and this was causing the CORS issues.

For people looking at this issue in the future, make sure you don't have any tracking library enabled, or other library that manipulate your http calls (like Azure msal for example)

Regards