There are not many stories of integrating Elm to existing projects, but there are some. We at Conta AS integrated Elm in our big AngularJS application. So Elm work side by side with AngularJS. It’s possible to embed Elm program to AngularJS code, and it’s possible to embed AngularJS component to Elm program. Which makes the communication part easy. It’s true for any other technology such as React, Vue, etc..