Garbage collector Mark And Sweep example in TS

gc-ms.ts

class GarbageCollector {
  public heap: Set<object>;

  constructor() {
    this.heap = new Set(); // Simulates the heap where all objects are stored
  }

  allocate(obj) {
    this.heap.add(obj); // Add the object to the heap
    return obj;
  }

  mark(root) {
    const visited = new Set();

    const traverse = (node) => {
      if (node && !visited.has(node)) {
        visited.add(node); // Mark the node as visited
        for (const key in node) {
          if (typeof node[key] === 'object') {
            traverse(node[key]); // Recursively traverse child objects
          }
        }
      }
    };

    traverse(root); // Start marking from the root object
    return visited;
  }

  sweep(marked) {
    for (const obj of this.heap) {
      if (!marked.has(obj)) {
        this.heap.delete(obj); // Remove unmarked objects from the heap
        console.log(
          `Object with value ${JSON.stringify(obj)} has been garbage collected.`
        );
      }
    }
  }

  collectGarbage(root) {
    console.log('Starting garbage collection...');
    const marked = this.mark(root); // Mark phase
    this.sweep(marked); // Sweep phase
    console.log('Garbage collection completed.');
  }
}

// Initialize garbage collector
const gc = new GarbageCollector();

// Step 1: Initialize object A
let A = gc.allocate({ value: 1 });

// Step 2: Add objects B, C, and D
let B = gc.allocate({ value: 2 });
A.B = B; // A points to B
A.C = gc.allocate({ value: 3 }); // A points to C
B.D = gc.allocate({ value: 4 }); // B points to D

// Step 3: Add object E to C
A.C.E = gc.allocate({ value: 5 }); // C points to E

// Simulate the heap and object structure
console.log('Heap after initialization:', Array.from(gc.heap));

// Step 4: Remove reference to B
delete A.B; // D becomes unreachable

// Perform garbage collection
gc.collectGarbage(A);

// Simulate the heap after garbage collection
console.log('Heap after garbage collection:', Array.from(gc.heap));