// TODO: handle null values
sS replaceDollarVars_js(S s, O... _) {
  //ret replaceDollarVars_withCustomToString(s, o -> jsonEncode_extended(o), _);
  MapSO vars = paramsToMap_withNulls(_);
  if (empty(vars)) ret s;
  var vars2 = mapKeys dropDollarPrefix(vars);
  
  ret replaceDollarVars_dyn(s, var -> {
    if (!vars2.containsKey(var)) null;
    O value = vars2.get(var);
    ret jsonEncode_extended(value);
  });
}

Began life as a copy of #1032133