const date = new Date;
const month = date.getMonth() + 1;
const day = date.getDay();
const dayNumber = date.getDate();
const weekDays = ['1 شنبه', '2 شنبه', '3 شنبه', '4 شنبه', '5 شنبه', 'آدینه', 'شنبه'];
const monthNames = ["January","February","March","April","May","June","July", "August","September","October","November","December"];

var weekDisplay = document.querySelector(".weekDisplay");
var wDisplayDay = document.querySelectorAll(".wDisplayDay");
var dayNumY = document.querySelectorAll(".dayNumY");
var dayNameX = document.querySelectorAll(".dayNameX");

function numOfDays(){                   
    // this function returns the number of days between today and the 1st of next month
    const oneDay = 24*60*60*1000        //hours*minutes*seconds*millseconds
    let start = new Date(date.getFullYear(), month - 1, dayNumber);
    let end = new Date(date.getFullYear(), month, 1)
    const diffDays = Math.round(Math.abs((start - end) / oneDay));
    return diffDays
}

function addDates(){
    var currentDays = numOfDays() + dayNumber;
    console.log(currentDays);  // should alway return the number of days in the current month
    for(var i = 0; i < currentDays; i++){
        console.log(dayNumY[i].textContent);
        dayNumY[i].textContent = dayNumber + Number([i]); 
    }
}
function addNames(){
    if(day > 0){
        let newArr = weekDays.slice(0, day);    // slices from "day 0 (sunday)", up to today - saved in newArr
        let newArr2 = weekDays.slice(day);      // slices from today to end of weekDays array - saved in newArr2
        let fixedArr = newArr2.concat(newArr);  // by adding newArr (sunday - today) to the end of newArr2 (today - saturday)
                                                // a new array is created using today as position zero. 
        for(var i = 0; i < fixedArr.length; i++){
            dayNameX[i].textContent = fixedArr[i];
        }
    } else {
        for(var i = 0; i < weekDays.length; i++){
            dayNameX[i].textContent = weekDays[i];
        }
    }
}
addNames();
addDates();