deadfish implementation in __defineGetter__

deadfish.js

// https://esolangs.org/wiki/Deadfish

$_ = function(e,v) { 
  var v = (v===undefined||v in {255:0,'-1':0})?0:v
  var e = e===undefined?'':e
  let x = {e:e,v:v}
  x.__defineGetter__('i', ((a,b)=>(()=>$_(a,++b)))(e,v))
  x.__defineGetter__('d', ((a,b)=>(()=>$_(a,--b)))(e,v))
  x.__defineGetter__('s', ((a,b)=>(()=>$_(a,b*b)))(e,v))
  x.__defineGetter__('o', ((a,b)=>(()=>$_(a+String.fromCodePoint(b),b)))(e,v))
  return x
}

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