let CO =
       { Target =
           < es3
           | es5
           | es6
           | es2015
           | es2016
           | es2017
           | es2018
           | es2019
           | es2020
           | esnext
           >
       , JSX = < preserve | react | react-native >
       , Module =
           < commonJS
           | amd
           | umd
           | system
           | es6
           | es2015
           | es2020
           | esnext
           | none
           >
       , Lib =
           < es5
           | es6
           | es7
           | es2015
           | es2016
           | es2017
           | es2018
           | es2019
           | es2020
           | esnext
           | dom
           | scripthost
           | webworker
           >
       }
 
 let JSConfigType =
       { compilerOptions :
           { target : CO.Target
           , jsx : CO.JSX
           , module : CO.Module
           , baseUrl : Text
           , allowSyntheticDefaultImports : Bool
           , noEmit : Bool
           , lib : List CO.Lib
           , rootDirs : List Text
           }
       , exclude : List Text
       }
 
 let JSConfig =
       { Type = JSConfigType
       , default =
           { compilerOptions =
               { target = CO.Target.es6
               , jsx = CO.JSX.preserve
               , module = CO.Module.es6
               , baseUrl = "src"
               , allowSyntheticDefaultImports = False
               , noEmit = True
               , rootDirs = [ "src" ]
               , lib = [ CO.Lib.dom ]
               }
           , exclude = [ "node_modules" ]
           }
       }
 
 in  JSConfig::{
     , compilerOptions = JSConfig.default.compilerOptions::{
       , rootDirs = [ "src" ]
       }
     }