Running ./gradlew run within a terminal show the following issue for both (ir, legacy) backend. However, the detailed message could look a bit different for each case:

# kotlin.js.compiler=legacy

> Task :nodeRun FAILED                                                                                                                                                                                                                                                                                          
Starting TaskApp                                                                                                                                                                                                                                                                                                
                                                                                                                                                                                                                                                                                                                
/anywhere/kotlin-js-es6-inheritance/src/main/kotlin/Main.kt:3                                                                                                                                                                                                                               
class TaskApp: App () {                                                                                                                                                                                                                                                                                         
               ^                                                                                                                                                                                                                                                                                                
TypeError: Class constructor App cannot be invoked without 'new'   

Information

1. The nvmrc file can be used to create a local environment using nvm install or nvm use, but it is not a requirement.
2. A sample npm project containing an es6 class export is linked as dependency and will be present in the node_modules build directory.
3. The actual kotlin definition has been created with dukat (./gradlew generateExternals). The content has then been manually copied and enhanced with a file:JsModule annotation at package level. It would otherwise not create the needed require('app') statement.