const createBtn = document.getElementById("create-btn");

function newTask() {
  let ul = document.getElementsByClassName("task-list");
  let li = document.createElement("li");
  let taskForm = document.getElementById("task-form");
  li.appendChild(document.createTextNode(taskForm.value));
  ul.appendChild(li);
}

createBtn.addEventListener("click", newTask);

<div class="input-wrapper">
          <input
            type="text"
            id="task-form"
            name="task-form"
            placeholder="Type something..."
          />
          <button id="create-btn" onclick="newTask()">
            Create Task
          </button>
        </div>