A constant expression can always be degenerated to a simpler constant form.

For example 100 + 101 is a constant expression, but could be replaced by the value 202.

A constant expression involving strings is "abcdef" + "ABCDEF". This yields the result "abcdefABCDEF".

Warnings:

• In JavaScript you should always try to avoid the use of string concatenation unless you really have to use it. It is very useful. However, in Netscape and MSIE, over-using a string concatenation in a loop can lead to significant memory leaks. It is quite easy to leak several megabytes of memory in a few minutes simply by concatenating strings and passing them to a document.write(). The garbage does eventually get collected, but not until the page is refreshed. This means that a page that implements a ticker for instance can leak horribly until the page is refreshed. There are techniques you can employ to minimize this effect and you could trigger a garbage collection by reloading the page periodically under script control.