document.head v. document.getElementsByTagName(“head”)[0]

Question

What is the difference between using document.head and using document.getElementsByTagName(\"head\")[0]? Tests I ran showed that they both take about a

Answer 1

Using the || operator like that is a form of feature detection. When used, if the first value is undefined it sends back the latter value.

So for

document.head || document.getElementsByTagName("head")[0];

the reason is that if document.head is not supported at least the right value is returned.

As for your speed test, a millisecond is a long time. I doubt it really took that long. In fact, I made a jsPerf for this. It shows that the getElementsByTagName function is roughly 80% slower.