script.js

const button =
document.getElementById('button');
const inputBox =
document.getElementById('input-box'); 
const listContainer =
document.getElementById('list');

button.addEventListener('click', function() {
  if(inputBox.value === ''){
    alert('Type 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();