I have added the li variable using querySelectorAll, but when I attempt to add an event listener to it to change the textDecoration style to line-through, I am not having any success. Any ideas?

// Variables
let addBtn = document.querySelector("#addBtn");
let input = document.querySelector("#input");
let ul = document.querySelector("ul");
let li = document.querySelectorAll("li");
let completeBtn = document.querySelector("#complete-btn");

// Functions
function inputLength() {
  return input.value.length;
}

function createListElement() {
  let li = document.createElement("li");
  li.appendChild(document.createTextNode(input.value));
  ul.appendChild(li);
  input.value = "";
}

function addListAfterClick() {
  if (inputLength() > 0) {
    createListElement();
  }
}

function addListAfterKeypress(e) {
  if (inputLength() > 0 && event.keyCode === 13) {
    createListElement();
  }
}

function done() {
  li.style.textDecoration = "line-through";
}

// Event Listeners
addBtn.addEventListener("click", addListAfterClick);

input.addEventListener("keypress", addListAfterKeypress);

// I would like to add an event listener here so that the li elements textDecoration is changed to "line-through"

completeBtn.addEventListener("click", function complete() {
  alert("Congratulations! You won't starve this week.");
  console.log(completeBtn);
  completeBtn.style.display = "none";
});