This code below works fine when i put a number after my eq.
 for (i=0; i<$("button.mark").length ; i++){
   $("button.mark:eq(0)").on("click", e => {
     e.preventDefault()
     e.stopPropagation()
     $("div.popup:eq(0)").show()
  
      if ($("div.popup:eq(0)").css("display") === "block") {
        $(window).on("click", () => {
          $("div.popup:eq(0)").hide()
        })
      }
   })
 }
but it stop working when i try to put it in the for with i. Do you know why ?
for (i=0; i<$("button.mark").length ; i++){
   $("button.mark:eq(i)").on("click", e => {
     e.preventDefault()
     e.stopPropagation()
     $("div.popup:eq(i)").show()
  
      if ($("div.popup:eq(i)").css("display") === "block") {
        $(window).on("click", () => {
          $("div.popup:eq(i)").hide()
        })
      }
   })
 }
