GARBAGE COLLECTION

JavaScript is a garbage-collected language, meaning that the execution environment is responsible for managing the memory required during code execution. In languages such as C and C++, keeping track of memory usage is a principle concern and the source of many issues for developers. JavaScript frees developers from worrying about memory management by automatically allocating what is needed and reclaiming memory that is no longer being used. The basic idea is simple: figure out which variables aren't going to be used and free the memory associated with them. This process is periodic, with the garbage collector running at specified intervals (or at predefined collection moments in code execution). The process of garbage collection is an approximate and imperfect solution because the general problem of knowing whether some piece of memory is needed is “undecidable,” meaning it cannot be solved by an algorithm.

Consider the normal life cycle of a local...