Currently working and testing the interaction of Unity WebGL projects with the browser side javascript, require builds. This makes the development iteration quite painful and time wasting. To make it worst, WebGL builds are slowww.
If we could have an option that for WebGL projects the Unity Editor would run an instance of a javascript engine and serve the jslib contents, that would make the in-editor play sessions entirely functional, and actually meaningful.
Right now, even for the slightest of interaction tests we need to make a build, and as said, development cycle is quite a pain.