Goal
Avoid unnecessary event bindings.
Sample code
Comment box with a reply button for each individual comment
const btns = document.getElementsByClassName('reply-btn');
for (let i = 0; i < btns.length; i++) {
btns[i].addEventListener('click', showCommentContentAsPreview);
}
function showCommentContentAsPreview(e) {
console.log('showCommentContentAsPreview()');
// CHECK IF THIS BUTTON ALREADY BINDED !!!
const previewDiv = document.getElementById('preview');
const commentId = e.target.getAttribute('data-comment-id')
const commentDiv = document.getElementById('comment-' + commentId);
const commentText = commentDiv.querySelector('p').innerText
const closeReplyBtn = previewDiv.querySelector('button');
const previewContent = previewDiv.querySelector('.preview-content');
// set to preview
previewContent.innerText = commentText;
// show reply close button
closeReplyBtn.classList.remove('hidden');
// bind EventListener to "reply close button"
closeReplyBtn.addEventListener('click', closeReply)
function closeReply() {
console.log('bind to btn');
previewContent.innerText = '';
this.removeEventListener('click', closeReply);
closeReplyBtn.classList.add('hidden');
}
}
.hidden {
display: none;
}
.comment {
border-bottom: 1px solid #000;
padding: 5px;
}
.preview {
background-color: #ccc;
padding: 20px;
margin-top: 20px;
}
<div>
<!-- comment list -->
<div id="comment-1" class="comment">
<p>Comment Content 1</p>
<button class="reply-btn" data-comment-id="1">reply</button>
</div>
<div id="comment-2" class="comment">
<p>Comment Content 2</p>
<button class="reply-btn" data-comment-id="2">reply</button>
</div>
</div>
<!-- output -->
<div>
<div id="preview" class="preview">
<div class="preview-content"></div>
<button class="hidden">Close Preview</button>
</div>
</div>
Simulate problem
When you try the example, the following two scenarios occur:
-
Click reply once and then click “close preview”
-
Click on reply several times and then on “close preview”.
Question
How can I avoid multiple bindings to the same button? I am already thinking about singleton.