To Do list with check button

I want to make my own To Do list using JavaScript and localStorage. After writing the input and pressing the send button, the item will be added and display on the screen. A check button will appear next to the item. After pressing the check button, I want the class to be added. I want add css (opacity, line...). But when I press a check button, the console shows this error: Uncaught TypeError: Cannot read properties of undefined (reading 'add') at check (app.js:23) at HTMLElement.onclick (index.html:30)

HTML code:

<body>
   <div class="main">
      <input id="item" type="text">
      <i id="addItem" class="fas fa-plus"></i><br> <br>
   </div>

   <div class="items">
      <div id="addedItems"></div>
   </div>
   <i onclick='deleteAll()' class="fas fa-trash"></i>
</body>

JS code:

const item = document.getElementById("item");
const add = document.getElementById("addItem");
const addedItems = document.getElementById("addedItems");

add.onclick = function() {
   const itemValue = item.value;
   const itemValue2 = ' ';

   if (itemValue && itemValue2) {
       localStorage.setItem(itemValue, itemValue2);
       location.reload();
   }
};

for (let a = 0; a < localStorage.length; a++) {
   const itemValue = localStorage.key(a);
   addedItems.innerHTML += `<div class= 'text'> <div>${itemValue}</div> <div> 
                            <i onclick='check("${itemValue}")' class="fas fa-check"></i><i 
                            onclick='deleteItem("${itemValue}")' class="fas fa-trash-alt"></i> 
                            </div></div> <br>`;

}

function check(itemValue) {
   itemValue.classList.add("mystyle");
}

function deleteItem(itemValue) {
  localStorage.removeItem(itemValue);
  location.reload();
}

function deleteAll() {
   localStorage.clear();
   location.reload();
}