What is better, appending new elements via DOM functions, or appending strings with HTML tags?
Some notes:
Using
innerHTML
is faster in IE, but slower in chrome + firefox. Here's one benchmark showing this with a constantly varying set of<div>
s +<p>
s; here's a benchmark showing this for a constant, simple<table>
.On the other hand, the DOM methods are the traditional standard --
innerHTML
is standardized in HTML5 -- and allow you to retain references to the newly created elements, so that you can modify them later.Because innerHTML is fast (enough), concise, and easy to use, it's tempting to lean on it for every situation. But beware that using
innerHTML
detaches all existing DOM nodes from the document. Here's an example you can test on this page.First, let's create a function that lets us test whether a node is on the page:
function contains(parent, descendant) { return Boolean(parent.compareDocumentPosition(descendant) & 16); }
This will return
true
ifparent
containsdescendant
. Test it like this:var p = document.getElementById("portalLink") console.log(contains(document, p)); // true document.body.innerHTML += "<p>It's clobberin' time!</p>"; console.log(contains(document, p)); // false p = document.getElementById("portalLink") console.log(contains(document, p)); // true
This will print:
true false true
It may not look like our use of
innerHTML
should have affected our reference to theportalLink
element, but it does. It needs to be retrieved again for proper use.
There are a number of differences:
innerHTML
has only been standardised by the W3C for HTML 5; even though it has been a de facto standard for some time now across all popular browsers, technically in HTML 4 it's a vendor extension that standards-adherent developers would never be caught dead using. On the other hand, it's much more convenient and practically it's supported by all browsers.innerHTML
replaces the current content of the element (it does not let you modify it). But again, you gain in convenience if you don't mind this limitation.innerHTML
has been measured to be much faster (admittedly, that test involves older versions browsers that are not widely used today).innerHTML
might represent a security risk (XSS) if it's set to a user-supplied value that has not been properly encoded (e.g.el.innerHTML = '<script>...'
).
Based on the above, it seems that a practical conclusion might be:
- If you don't mind the fact that
innerHTML
is a bit limiting (only total replacement of DOM sub-tree rooted at target element) and you don't risk a vulnerability through injecting user-supplied content, use that. Otherwise, go with DOM.