Review
- 2024-07-28 19:53
[!Summary]
- Garbage collection is performed automatically. We cannot force or prevent it.
- Objects are retained in memory while they are reachable.
- Being referenced is not the same as being reachable (from a root): a pack of interlinked objects can become unreachable as a whole, as we’ve seen in the example above.
一、Introduction #
Low-level languages like C, have manual memory management primitives such as malloc() and free(). In contrast, JavaScript automatically allocates memory when objects are created and frees it when they are not used anymore (garbage collection). This automaticity is a potential source of confusion: it can give developers the false impression that they don’t need to worry about memory management.
Regardless of the programming language, the memory life cycle is pretty much always the same:
- Allocate the memory you need
- Use the allocated memory (read, write)
- Release the allocated memory when it is not needed anymore
The following “garbage collection” steps are regularly performed:
- The garbage collector takes roots and “marks” (remembers) them.
- Then it visits and “marks” all references from them.
- Then it visits marked objects and marks their references. All visited objects are remembered, so as not to visit the same object twice in the future.
- …And so on until every reachable (from the roots) references are visited.
- All objects except marked ones are removed.
Reference #
Garbage collection https://javascript.info/garbage-collection Memory management https://developer.mozilla.org/en-US/docs/Web/JavaScript/Memory_management The lifecycle of Memory in JavaScript