如何在单击事件监听器中删除按钮的轮廓？

Question

以下是按钮的事件监听器，我正在尝试删除按钮的轮廓以及其他内容...

btn.addEventListener('click', boom)
function boom () {
    let input2 = input.value;
    document.querySelector('.btn').style.outline = "none" //THIS IS THE LINE
    if (input2 === '') {
        alert("You Can't Enter an Empty Value") 
        output.innerHTML = output.innerHTML; 
    }
    else {
    output.innerHTML = input2;
    input.value = '';
}
    }

但是此行不起作用

document.querySelector('.btn').style.outline = "none"