JSFiddle - React, Tailwind, and code Playground

HTML

<div id="status">
</div>

JavaScript

var students = {"A": [], "B": [], "C":[]};
var weeks = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"];


function AssignWeeks() {
  var slength = Object.keys(students).length;
  var wlength = weeks.length;
var sIndex = 1;
  for (var skey in students) {
    var wIndex = sIndex;
    while (wIndex <= wlength) {
      students[skey].push(wIndex);
      wIndex += slength;
    }

sIndex++;
  }
}


AssignWeeks();
document.getElementById("status").innerHTML = JSON.stringify(students);