If JS code creates a structure or an array, that memory will be valid as long as the JS object stays alive. Pointers to that memory must be carefully managed to make sure the underlying memory is still referenced.
When binary code hands back a pointer/handle to allocated memory, the JS code must make sure to free that memory with the correct allocator. It is usually best to expose a freeing function from the binary.
The following js-ctypes objects will hold references to objects, keeping them alive. This is not an exhaustive list, but will help you to understand memory management and how it affects your use of js-ctypes:
declare() method will hold that library alive.
CType will hold referent
CType objects alive.
CData will hold referent
CData objects alive, under specific circumstances. For example, a
CData object produced by accessing a field of a structure or the internals of an array will hold the referent objects alive.
It's important to note that getting direct access to the contents of a
CData object using
contents, will result in a
CData object that does not hold its referent alive. Be sure to hold an explicit reference so that the referent object doesn't get into garbage collection, before you're done using it.
When you need to keep data around, you can use