JSFiddle - React, Tailwind, and code Playground

JavaScript

function DATE_OBJ (iyear,imonth,iday,idirty,ijd) {
    this.Year = iyear;
    this.Month = imonth;
    this.Day = iday;
    this.Dirty = idirty;
    this.JD = DateJD;
}

function DateJD() {
    var Y = objDate.Year;
    var M = objDate.Month;
    var D = objDate.Day;
    
    if (M < 3) {
        --Y;
        M +=12;
    }
    
    if (objDate.Year > 1582) {
    
      var A = parseInt(Y / 100, 10);
      var B = 2 - A + parseInt(A / 4,10);
      } else {
        if (objDate.Year = 1582 && M > 10) {
          var A = parseInt(Y / 100, 10);
          var B = 2 - A + parseInt(A / 4,10);
          } else {
            if (objDate.Year = 1582 && M = 10 && D >=15) {
              var A = parseInt(Y / 100, 10);
              var B = 2 - A + parseInt(A / 4,10);
              } else var B = 0;
          }
        }
 
    if (Y < 0) var C = parseInt((365.25 * Y) - 0.75,10);
    else var C = parseInt(365.25 * Y,10);
        
    var E = parseInt(30.6001 * (M + 1),10);
    
    return B + C + E + objDate.Day + 1720994.5;
}
 

var d = new Date();    
var objDate = new DATE_OBJ (d.getFullYear(),d.getMonth(),d.getDate(),false,0);

document.write(objDate.JD());