jsbin.nitoqu.js

// working with a csv date with an unknown number of characters 
// can be 7 characters if day is only 1 character long
// or it'll be 8 characters if day is 2 characters long

//var csvDate = "12231991";

function getDateFromString(csvDate) {
  var myYear = 0;
  var myMonth = 0;
  var myDay = 0;

  myYear = csvDate.slice(-4);

  myMonth = csvDate.slice(-6, -4);

  if (csvDate.length === 7) {
    myDay = "0" + csvDate.slice(0,1);
  } else if (csvDate.length === 8) {
    myDay = csvDate.slice(0,2);
  } else {
    return console.log("There is an error");
  }

  console.log(myYear);
  console.log(myMonth);
  console.log(myDay);
  console.log(myDay + "/" + myMonth + "/" + myYear);
}

getDateFromString("2101202");