querySelector (GetElementByID) - Multiple IDs

Question

i have function to convert gregorian dates to jalali date,its work for one tag,but i have unspecified number of this tags in one page, and it must convert all of theme.

Answer 1

You made mistakes in your code, also in the DOM, you do not have two elements with the same identifier. The querySelector returns that the first element found, you must instead use querySelectorAll which will return you an array.

function gregorian_to_jalali(gy,gm,gd){
 g_d_m=[0,31,59,90,120,151,181,212,243,273,304,334];
 if(gy > 1600){
  jy=979;
  gy-=1600;
 }else{
  jy=0;
  gy-=621;
 }
 gy2=(gm > 2)?(gy+1):gy;
 days=(365*gy) +(parseInt((gy2+3)/4)) -(parseInt((gy2+99)/100)) +(parseInt((gy2+399)/400)) -80 +gd +g_d_m[gm-1];
 jy+=33*(parseInt(days/12053)); 
 days%=12053;
 jy+=4*(parseInt(days/1461));
 days%=1461;
 if(days > 365){
  jy+=parseInt((days-1)/365);
  days=(days-1)%365;
 }
 jm=(days < 186)?1+parseInt(days/31):7+parseInt((days-186)/30);
 jd=1+((days < 186)?(days%31):((days-186)%30));
 return [jy,jm,jd];
}

var dateElement = document.querySelectorAll('.date');
for(var i = 0; i < dateElement.length; i++) {
  const year = Number(dateElement[i].dataset.year); // "2019"
  const month = Number(dateElement[i].dataset.month); // "2"
  const day = Number(dateElement[i].dataset.day); // "6"
  dateElement[i].textContent = gregorian_to_jalali(year, month, day).join('/');
}