Error

const btn = document.querySelector("[data-form-btn]");

const createTask = (evento) => {    
    evento.preventDefault();
    const input = document.querySelector("[data-form-input]");
    const value = input.value; 
    const list = document.querySelector("[data-list]")
    const task = document.createElement("li");
    task.classList.add("card");
    input.value = "";
    console.log(checkComplete());
    //backticks
    const taskContent = document.createElement("div");
    taskContent.appendChild(checkComplete());
    const titleTask = documen.createElement("span");
    titleTask.classList.add("task");
    titleTask.innerText = value;
    taskContent.appendChild(titleTask);
    const content = `
        <i class="fas fa-trash-alt trashIcon icon"></i>`;
    //task.innerHTML = content;
    task.appendChild(taskContent);
    list.appendChild(task);

    console.log(content);
};

console.log(btn);

btn.addEventListener("click", createTask);

const checkComplete = () => {
    const i = document.createElement("i");
    i.classList.add("far");
    i.classList.add("fa-check-square");
    i.classList.add("icon");
}

Hola, hago paso a paso como en el video, pero a la hora de probrar el codigo, me marca un error, quisiera saber a que se debe.

Uncaught TypeError: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'. at HTMLButtonElement.createTask