script.js

const inputBox= document.getElementById("input-box");
const listcont= document.getElementById("list");
function AddTask(){
    if(inputBox.value === ''){
        alert("You must have to something");
    }
    else{
        let li = document.createElement("li");
        li.innerHTML= inputBox.value;
        listcont.appendChild(li);
        let span= document.createElement("span")
        span.innerHTML= "\u00d7";
        li.appendChild(span);
    }
    inputBox.value= ''
    savedata();
}
listcont.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", listcont.innerHTML)
}
function showcase(){
    listcont.innerHTML=localStorage.getItem("data");
}
showcase();