JScript uses a mark-and-sweep garbage collector with a variety of heuristics used to determine when to run garbage collection. The JScript garbage collector works like this:
1、When the script engine is shut down, garbage is collected.
2、When 256 variants, or more than 64KB of strings, or more than 4096 array slots have been allocated, the garbage collector sets a flag that says collect soon.
3、Whenever a new statement is executed or the script debugger starts, that flag is checked, and if it is set, a collection is done.
There is an undocumented JScript function called CollectGarbage that forces a garbage collection. This is for testing purposes only—do not ship code that calls this function. It is a poor programming practice to write code in JScript that depends on garbage collections being done at particular times. If you need predictable garbage collection, use a language that supports it (like Visual Basic? or VBScript). Note that all of this is the implementation detail of the engine and should not be relied upon because it may change in the future. Note also that the version of JScript supported by Microsoft? .NET will use the .NET Framework garbage collector, a multigenerational mark-and-sweep collector.
And remember, if you want a deterministic-lifetime app, use a deterministic-lifetime language like C++, Visual Basic 6.0, or VBScript; not an indeterministic-lifetime language like JScript, Scheme, or Java. If you're writing a program that depends on being able to have a deterministic object lifetime, JScript is not the right tool for the job. Trying to make it a deterministic-lifetime language will just create headaches down the road.
js的内存管理类似于java的内存管理！你可以参看java的内存管理机制。
释放一个对象所占的内存必须先释放所有对该对象的引用。
但当对象没有被任何变量应用时，browse也不一定释放该对象所占的内存。
CollectGarbage()并不是推荐的方法。
ie最小化时，会进行垃圾回收！
