If you use the Dynatrace oneAgent with auto injection of the JavaScript tag, you can use one single JavaScript library if both applications have the same configuration like XHR frameworks or some of the advanced configuration settings. Even the auto injected JavaScript tag can differ, the JS agent might be the same (but only if for both applications the same XHR frameworks and other content capture features are applied).
The same applies for manual injected (agentless monitoring) application where you have to insert the RUM JavaScript tag. The tag must be different for two different applications, but the JavaScript file might be the same.
