const EXPLODE_CHAR = "#";

/*
 Loop through every item inside the array
 */
for (var index = 0; index < dataNoordHolland.length; index++) {
    /*
     Explode every item by the # character to convert it to an array
     */
    var splittedItem = dataNoordHolland[index].split(EXPLODE_CHAR);
    splittedItem.splice(1, 0, "Item i want to add to teh array!");
    console.log(splittedItem);
}