How can I add an error msg for This To-DO list problem

HTML
“

Add
“`
JS

function addTask(){
    if(inputBox.value === ''){
        document.getElementById("errmsg").innerHTML = "You Must Write Somthing!";
        return false;
    }
    else{
        let li = document.createElement("li");
        li.innerHTML = inputBox.value;
        listContainer.appendChild(li);
        let span = document.createElement("span");
        span.innerHTML = "×";
        li.appendChild(span);
    }
    inputBox.value = '';
    saveData();
}

I want to give an error in the placeholder, but it’s overwriting (https://i.sstatic.net/oT2UfccA.png) I’m new in JS, so I didn’t get how to fix it plz help me 🙁