Object Lifecycle

Introduction

Every object in a program goes through a lifecycle: from the moment it’s created (memory allocated) to the moment it’s destroyed (memory reclaimed). Understanding this lifecycle is crucial for writing efficient, leak-free code.

The Object Lifecycle Stages

stateDiagram-v2
    [*] --> Declaration: Variable declared
    Declaration --> Allocation: new keyword
    Allocation --> Initialization: Constructor called
    Initialization --> Usage: Object ready
    Usage --> Unreachable: No more references
    Unreachable --> GC: Garbage collector runs
    GC --> [*]: Memory reclaimed

Stage Details

Stage	What Happens
Declaration	Reference variable created (null/undefined)
Allocation	Memory allocated on heap
Initialization	Constructor runs
Usage	Methods called, properties accessed
Unreachable	No more references to the object
GC	Memory reclaimed (non-deterministic timing)

Example

class Resource {
  constructor(name) {
    this.name = name;
    this.id = ++Resource.instanceCount;
  }
  use() { /* using the object */ }
  dispose() { /* cleanup logic */ }
}

// Lifecycle
let res = new Resource("DB Connection"); // Created + Initialized
res.use();                                // Used
res.dispose();                            // Manual cleanup
res = null;                               // Eligible for GC

Best Practices

Clean up resources explicitly — close files, connections, sockets
Don’t rely on finalizers/destructors — they’re not deterministic
Nullify references to help GC (in long-lived collections)

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