script.js

const inputBox = document.getElementById("inputTask")
const listContainer = document.getElementById("taskList")

function addTask() {
    if (inputBox.value === '')
    {
        alert("The input can`t be empty!");
    } 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);