timeschedule.js

var TimeSchedule = function() {
  this.timeSchedule = [
    [], [], [], [], [], [], []
  ];
};

TimeSchedule.prototype = {
  setLesson: function(day, period, lesson) {
    if (!this.timeSchedule[day][period-1]) {
      this.timeSchedule[day][period-1] = lesson;
    }
  },
  getLesson: function(day, period) {
    if (period) {
      return this.timeSchedule[day][period-1];
    } else {
      return this.timeSchedule[day];
    }
  },
  deleteLesson: function(day, period) {
    if (this.timeSchedule[day][period-1]) {
      this.timeSchedule[day][period-1] = null;
    }
  }
};