How to delete the contents of a paragraph with javascript

I have a paragraph that I'd like to delete the contents of.

document.getElementById(id).innerHTML = "";

doesn't seem to be working. Does anyone have a better solution?

Here's an example

<!DOCTYPE html>
<html>
<head>
<script>
document.getElementById("p").innerHTML = "";
</script>
</head>
<body>
<p id="p">
words
</p>
</body>
</html>

but the words in the paragraph are not removed. Thanks in advance to anyone that can help.

Solution

<!DOCTYPE html>
<html>
<head>
<!-- here the p tag doesn't exist yet -->
<script>
document.getElementById("p").innerHTML = "";
</script>
</head>
<body>
<p id="p">
words
</p>

<!-- however here it does exist -->
</body>
</html>

how to fix it ?

// only use this if you can't move your javascript at the bottom
window.onload = function() {
    document.getElementById("p").innerHTML = "";
}

or move your javascript at the end of the page (this is the preferred one as javascript should always be loaded at the end of the page)

<!DOCTYPE html>
<html>
<head>
<!-- here the p tag doesn't exist yet -->

</head>
<body>
<p id="p">
words
</p>

<!-- however here it does exist -->
<script>
document.getElementById("p").innerHTML = "";
</script>
</body>
</html>