Infinite Scrolling with a strange bug

I got on the internet a infinite scrolling script, however it was in jQuery... and since I don't like jquery, I decided to change it to pure JS. When I replaced this $(window).on for this window.addEventListener and this $(window).off("scroll"); for this window.removeEventListener("scroll",... and a bug appeared:

Code running with jQuery - working very well:

<div class="post-item" id="8">8</div>
<div class="post-item" id="7">7</div>
<div class="post-item" id="6">6</div>
<div class="post-item" id="5">5</div>
<div class="post-item" id="4">4</div>
<div class="post-item" id="3">3</div>
<div class="post-item" id="2">2</div>
<div class="post-item" id="1">1</div>

windowOnScroll();
function windowOnScroll() {
  $(window).on("scroll", function(e){
    const {scrollHeight,scrollTop,clientHeight} = document.documentElement
    if (scrollTop + clientHeight > scrollHeight -5){
      if(document.querySelectorAll(".post-item").length < document.getElementById("total_count").value) {
        var lastId = document.querySelectorAll(".post-item");
        var lastchild = lastId[lastId.length-1];
        var id=lastchild.getAttribute("id");
        getMoreData(id);
      }
    }
  });
}
function getMoreData(id) {
  $(window).off("scroll");
  document.querySelector('.ajax-loader').classList.remove("none");
  var formdata=new FormData();
  formdata.append("lastId",id);
  fetch('getMoreData.php',{
    method: 'POST',
    body:formdata
  }).then(function(response){
    response.text().then(function(result){
      setTimeout(function() {
        document.querySelector('.ajax-loader').classList.add("none");
        document.getElementById("post-list").innerHTML+=result;
        windowOnScroll();
      }, 1000);
    })
  }).catch(function(err){ 
    console.error(err);
  });
}

Code running with JS pure - working NOT very well:

<div class="post-item" id="8">8</div>
<div class="post-item" id="7">7</div>
<div class="post-item" id="6">6</div>
<div class="post-item" id="5">5</div>
<div class="post-item" id="4">4</div>
<div class="post-item" id="3">3</div>
<div class="post-item" id="2">2</div>
<div class="post-item" id="4">4</div>
<div class="post-item" id="3">3</div>
<div class="post-item" id="2">2</div>
<div class="post-item" id="4">4</div>
<div class="post-item" id="3">3</div>
<div class="post-item" id="2">2</div>

windowOnScroll();
function windowOnScroll() {
  window.addEventListener("scroll", function(e){
    const {scrollHeight,scrollTop,clientHeight} = document.documentElement
    if (scrollTop + clientHeight > scrollHeight -5){
      if(document.querySelectorAll(".post-item").length < document.getElementById("total_count").value) {
        var lastId = document.querySelectorAll(".post-item");
        var lastchild = lastId[lastId.length-1];
        var id=lastchild.getAttribute("id");
        getMoreData(id);
      }
    }
  });
}
function getMoreData(id) {
  window.removeEventListener("scroll", windowOnScroll());
  document.querySelector('.ajax-loader').classList.remove("none");
  var formdata=new FormData();
  formdata.append("lastId",id);
  fetch('getMoreData.php',{
    method: 'POST',
    body:formdata
  }).then(function(response){
    response.text().then(function(result){
      setTimeout(function() {
        document.querySelector('.ajax-loader').classList.add("none");
        document.getElementById("post-list").innerHTML+=result;
        windowOnScroll();
      }, 1000);
    })
  }).catch(function(err){ 
    console.error(err);
  });

I'm using MYSQL and PHP on the server side.

Any idea to help me???

DEMO

Solution

Indeed, the problem was not that.. try this now, I added logic to not make other call until it finishes loading.

<!DOCTYPE html>
<html>
  <head>
    <title>How to Create Facebook Like Infinite Scroll Pagination using PHP and jQuery</title>
    <style type="text/css">
      body {
        font-family: Arial;
        background: #e9ebee;
        font-size: 0.9em;
      }

      .post-wall {
        background: #fff;
        border: #e0dfdf 1px solid;
        padding: 20px;
        border-radius: 5px;
        margin: 0 auto;
        width: 500px;
      }

      .post-item {
        padding: 10px;
        border: #f3f3f3 1px solid;
        border-radius: 5px;
        margin-bottom: 30px;
      }

      .post-title {
        color: #4faae6;
      }

      .ajax-loader {
        display: block;
        text-align: center;
      }
      .none {
        display: none;
      }
      .ajax-loader img {
        width: 50px;
        vertical-align: middle;
      }
    </style>
  </head>
  <body>
    <div class="post-wall">
      <div id="post-list">
        <input type="hidden" name="total_count" id="total_count" value="22" />

        <div class="post-item" id="22">
          <p class="post-title">Ajax live search using jQuery Ajax and PHP</p>
          <p>Ajax live search is a search form where you get search results instantly while you type. Therefore i</p>
        </div>
        <div class="post-item" id="21">
          <p class="post-title">Live image preview before upload to the server using jQuery</p>
          <p>Sometimes it is required to verify the selected image before upload it to the server. So, in this tu</p>
        </div>
        <div class="post-item" id="20">
          <p class="post-title">Count words and characters using jQuery</p>
          <p>A simple, word and character counter for HTML textarea and other input fields. The following simple</p>
        </div>
        <div class="post-item" id="19">
          <p class="post-title">Write data into CSV file using PHP</p>
          <p>Sometimes we need to generate CSV file containing data from database table. So, in this tutorial, we</p>
        </div>
        <div class="post-item" id="18">
          <p class="post-title">Read CSV file using PHP</p>
          <p>Read CSV file using PHP is very easy and simple. PHP has a built function fgetcsv(), through which w</p>
        </div>
      </div>
      <div class="ajax-loader none text-center"><img src="LoaderIcon.gif" /> Loading more posts...</div>
    </div>

    <script type="text/javascript">
      var isLoading = false;

      window.addEventListener("scroll", function () {
        const { scrollHeight, scrollTop, clientHeight } = document.documentElement;
        if (
          scrollTop + clientHeight > scrollHeight - 5 &&
          document.querySelectorAll(".post-item").length < document.getElementById("total_count").value
        ) {
          var lastId = document.querySelectorAll(".post-item");
          var lastchild = lastId[lastId.length - 1];
          var id = lastchild.getAttribute("id");
          getMoreData(id);
        }
      });

      function getMoreData(id) {
        if (isLoading) return;

        isLoading = true;

        document.querySelector(".ajax-loader").classList.remove("none");
        var formdata = new FormData();
        formdata.append("lastId", id);
        fetch("getMoreData.php", {
          method: "POST",
          body: formdata,
        })
          .then(function (response) {
            response.text().then(function (result) {
              setTimeout(function () {
                document.querySelector(".ajax-loader").classList.add("none");
                document.getElementById("post-list").innerHTML += result;
                isLoading = false;
              }, 1000);
            });
          })
          .catch(function (err) {
            console.error(err);
            isLoading = false;
          });
      }
    </script>
  </body>
</html>