Why document.write(“-->”) does not work as expected?

[PaulTheTree]

\[code\]<p>hello</p><script type="text/javascript">document.write("<!--");</script><p>world</p><script type="text/javascript">document.write("-->");</script><p>nihao</p>\[/code\]I thought the output of this piece of HTML is \[code\]hellonihao\[/code\]But it turns out as below:\[code\]hello");nihao\[/code\]How should I achieve what I expected? What's the problem here?