There are two objects with cyclic references to each other. Will this cause a memory leak? How does the garbage collector in JavaScript work and what is the main condition for memory cleanup?

In JavaScript, having two objects with cyclic references to each other does not necessarily cause a memory leak. Modern garbage collectors (GC) in JS use algorithms based on reachability analysis of objects, not just reference counting.

How the garbage collector works in JavaScript

The garbage collector tracks objects that are reachable from root points, such as global objects, call stacks, and closures. If an object is not reachable from these roots, it is considered garbage and can be collected.

Main condition for memory cleanup

An object will be removed by the garbage collector if there are no reachable references to it from the roots. Cyclic references between objects do not prevent collection if these objects are unreachable from outside.

Example:

function createCycle() {
  let objA = {};
  let objB = {};
  objA.ref = objB;
  objB.ref = objA;
  return 'done';
}
createCycle();
// After the function executes, objA and objB are unreachable from the roots, and the garbage collector will clean them up despite the cyclic reference.

Thus, cycles do not cause memory leaks by themselves if the objects are not held in a reachable state.