Pretty WebExtension APIs

API.js

this.MyAPI = class extends ExtensionAPI {
  getAPI(context) {
    const sandbox = Cu.Sandbox(context.cloneScope, {
      sameZoneAs: context.cloneScope,
      wantComponents: false,
      wantXrays: false
    })

    const init = Cu.evalInSandbox(function() {
      class MyThing {
        constructor(id) {
          this.id = id
        }
        open() {
          return this
        }
        close() {
          return this
        }
        [Symbol.iterator] {
          throw Error("Not Implemented")
        }
      }

      return {MyThing}
    }, sandbox)
    
    const api = init()

    return {
      MyAPI: {
        createMyThing(options) {
          return new api.MyThing()
        }
      }
    }
  }
}