What are the drawbacks of accessing DOM elements directly by ID?
Question
Today I stumbled upon the possibility to access a DOM element in Javascript simply by its id eg like this:
elementid.style.backgroundColor = "blue"
I tested with a very short snippet if this works in IE, Firefox and Chrome - and it does. Here is the snippet I used:
<html><head>
<script>
function highlight() {
content.style.backgroundColor = "blue";
content.style.color = "white";
}
</script>
</head>
<body>
<div id="content">test content</div>
<div onclick="highlight()">highlight content</div>
</body></html>
So I wondered in which cases document.getElementById('elementid') should be used (or similar framework replacements like $()) and what are the drawbacks of the direct access.
I was not able to find any useful documentation on this. Everywhere either getElementById or framework methods are used.
3 answers
solution1
7 ACCPTED 2009-07-08 10:26:20
It is propriety Microsoft gubbins. It doesn't work in lots of browsers — especially in standards mode (and you want standards mode to avoid quirks mode inconsistencies such as IE getting width wrong).
solution2
4 2009-07-08 10:42:03
You should also be concerned about name space. Right now you're treating it as if it's a variable in the global name space, and you would have to trust neither you nor any libraries that you include declare any global variables with the same name as DOM id's. The same goes for your highlight function.
Also while id's with dashes are perfectly valid, those would be inaccessible via this method.
eg <div id="container-wrapper"><div id="container"> ... </div></div>
would become container-wrapper.style.color which would then try to subtract wrapper.style.color from container.
solution3
2 2009-07-08 10:44:19
It's not a part of any standard. Besides, simple variables can be overwriten. Var content could be redeclared in any place of your script, or external library (and, yes, I know global variables are evil, but ppl still use them…) and your script will break.
And, naturally, you cannot use IDs like alert or document etc.
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