app.js

const inputBox = document.getElementById("input-text");
const listContainer = document.getElementById("list-container");

function addTask() {
    if (inputBox.value === '') {
        alert("You Must Write Something!");
    } else {
        let li = document.createElement("li");
        li.innerHTML = inputBox.value;
        listContainer.appendChild(li);
        let span = document.createElement("span");
        span.innerHTML = "\u00d7";
        li.appendChild(span);
    }
    inputBox.value = "";
    saveData();
}
listContainer.addEventListener("click",function(e){
    if (e.target.tagName === "LI"){
        e.target.classList.toggle("checked")
        saveData();
    } 
    else if(e.target.tagName === "SPAN") {
        e.target.parentElement.remove()
        saveData()
    }
} , false);

function saveData() {
    localStorage.setItem("data", listContainer.innerHTML);
}
function showTask() {
    listContainer.innerHTML = localStorage.getItem("data"); 
}
showTask();