How Do I Get An Html Comment With Javascript
Solution 1:
Using a NodeIterator (IE >= 9)
The best method is to use a dedicated NodeIterator instance iterating all comments contained in a given root element.
functionfilterNone() {
returnNodeFilter.FILTER_ACCEPT;
}
functiongetAllComments(rootElem) {
var comments = [];
// Fourth argument, which is actually obsolete according to the DOM4 standard, is required in IE 11var iterator = document.createNodeIterator(rootElem, NodeFilter.SHOW_COMMENT, filterNone, false);
var curNode;
while (curNode = iterator.nextNode()) {
comments.push(curNode.nodeValue);
}
return comments;
}
window.addEventListener("load", function() {
console.log(getAllComments(document.body));
});
Using a custom-made DOM traversal (to support IE < 9 as well)
If you have to support older browsers (e.g. IE <9), you need to traverse the DOM yourself and extract those elements whose node type is Node.COMMENT_NODE
.
// Thanks to Yoshi for the hint!// Polyfill for IE < 9if (!Node) {
var Node = {};
}
if (!Node.COMMENT_NODE) {
// numeric value according to the DOM spec
Node.COMMENT_NODE = 8;
}
function getComments(elem) {
var children = elem.childNodes;
var comments = [];
for (var i=0, len=children.length; i<len; i++) {
if (children[i].nodeType == Node.COMMENT_NODE) {
comments.push(children[i]);
}
}
return comments;
}
Extracting a node's contents and delete it
Independent of the way you choose from above, you receive the same node DOM objects.
Accessing a comment's contents is as easy as commentObject.nodeValue
.
Deleting a comment is a bit more verbose: commentObject.parentNode.removeChild(commentObject)
Solution 2:
You have to travers the DOM to get it.
The nodeType
of the comment DOM element is 8
if( oNode.nodeType === 8 ) {
oNode.parentNode.removeChild( oNode );
}
would be an approach
Solution 3:
Here is a JQuery plugin that retrieves the comments:
The basic idea is to look at nodes
, not elements
:
http://www.w3schools.com/htmldom/dom_nodes.asp
You start with document
object, and iterate through them using childNodes
collection. You have to check for node.nodeType == 8
which will return just the comment nodes (note that you need to iterate through child nodes recursively).
Solution 4:
I needed to store a template for an entire web page. But the <template>-tag cannot contain for example an <html>-tag. So I decided to store my template inside an HTML-comment instead.
I put the HTML-comment in a hidden <div> in order to more easily retrieve the text in that specific HTML-comment, and not have to bother with distinguishing it from other HTML-comments.
Here is a demo of how you can retrieve what's inside a HTML-comment by using createTreeWalker.
alert(
document.createTreeWalker(
document.getElementById('commentDiv'),
NodeFilter.SHOW_COMMENT,
null,
false
).nextNode().nodeValue
);
<p>Getting the text in a HTML-comment.</p><p>I use createTreeWalker to make sure we don't simply capture an empty text node by mistake. You could make the code even simpler, but then you must make sure that the <div>-tag is immediately followed by the "<!--", like this "<div><!--". But if that breaks because of for example autoformating in an editor, so that you get a line feed in between or so, then the simpler method will fail. That is why I prefere to use the createTreeWalker here.</p><!--
This is NOT the comment we want to get text from
--><divid="commentDiv"style="display:none;"><!--
This is THE text, and you can have anything in here
<>
<div>
<script>alert('hello');</script>
etc.
except of course an end of HTML-comment.
An advantage of this way to store a template compared to using
the <template>-tag, is that the <template>-tag can for example
not contain a <html>-tag, in case you need to have a template
for an entire web page.
Check also my explanation down in the body text for why I use
createTreeWalker instead of some simpler code.
--></div><!--
This is also NOT the comment we want to get text from
--><p>End of body.</p>
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