javascript - 在 Javascript 中隐藏 previous sibling 姐妹

Question

HTML:

<label>First Name</label>
<input type="text" value="" id="FNAME">

JS:

var FNAME = document.getElementById('FNAME');

FNAME.addEventListener('input', function() {
  if (FNAME.value !== ''){
    alert('Field not empty! Value: '+ FNAME.value);
    document.getElementById('FNAME').previousSibling.style.visibility = "hidden";
  }
});

...给出错误:

TypeError: undefined is not an object (evaluating 'FNAME.previousSibling.style')

我做错了什么？

Answer 1

再次将 previousSibling 附加到 previousSibling。它现在应该正确定位标签。

  var FNAME = document.getElementById('FNAME');
  if (FNAME.value !== ''){
    var label = FNAME.previousSibling.previousSibling.style.visibility = "hidden";
  }