nestedListMatch - Recursive

var nestedListMatch = function(lists, match) {

  var firstItem = lists[0];

  if(firstItem === match) {
    return match;
  }else if (Array.isArray(firstItem)){

    var result = nestedListMatch(firstItem, match)
    if(result === match) {
      return match;
    }
  }

  var newList = lists.slice(1);

  return (newList.length>0) ? nestedListMatch(newList, match) : null;
}

var nestedList = [[1,2,[3,4,5]], 6, 9];
console.log(nestedListMatch(nestedList, 2))
console.log(nestedListMatch(nestedList, 5))
console.log(nestedListMatch(nestedList, 9))