A recursive algorithm to get all the possibilities of a binary string after filling in placeholders

binaryCombos.js

function binaryCombos(str){
  var placeholder = "_";
  var result = [];
  if (!str.includes(placeholder)){
    result.push(str);
    return result;
  }
  for(var x = 0; x < str.length; x += 1){
    if (str[x] == placeholder){
      result = result.concat(binaryCombos(str.slice(0,x) + "0" + str.slice(x+1)));
      result = result.concat(binaryCombos(str.slice(0,x) + "1" + str.slice(x+1)));
      break;
    }
  }
  return result;
}