Elm vs ANTLR javascript

BoolExpr.elm

module BoolExpr where

type BExpr 
  = BTrue
  | BFalse 
  | BAnd BExpr BExpr
  | BOr BExpr BExpr

-- Example of (1 /\ (0 \/ 1)) AST: 
expr = BAnd BTrue (BOr BFalse BTrue)

-- Example of AST - driven view. We could simply extend this example from String to Html
view : BExpr -> String
view expression = 
  case expression of
    BTrue -> "1"
    BFalse -> "0"
    BAnd a b -> "(" ++ view a ++ " /\\ " ++ view b ++ ")"
    BOr a b -> "(" ++ view a ++ " \\/ " ++ view b ++ ")"
    

BoolExpr.js

// naive approach

var expr = { _type : "BoolExpr", _const : "And"
           , values : [ { _type : "BoolExpr", _const : "True", values : {} }
                      , { _type : "BoolExpr", _const : "Or"
                        , values : [ { _type : "BoolExpr", _const : "False", values : {} }
                                   , { _type : "BoolExpr", _const : "True", values : {} }
                                   ]
                        }
                      ]
           }

function view(expr) {
    switch(expr._const){
        case "True":
            return "1";
        case "False":
            return "0";
        case "And":
            return "(" + view(expr.values[0]) + " /\\ " + view(expr.values[1]) + ")";
        case "Or":
            return "(" + view(expr.values[0]) + " \\/ " + view(expr.values[1]) + ")";
    }
}