JavaScript Memory Management: V8 Garbage Collection Deep Dive | DevPrep

JavaScript Memory Management: V8 Garbage Collection Deep Dive | DevPrep

V8 Heap
├── New Space (Young Generation) — ~1-8MB
│   ├── Semi-space A (From-space)
│   └── Semi-space B (To-space)
└── Old Space (Old Generation) — up to GBs
    ├── Old Pointer Space (objects with pointers)
    ├── Old Data Space (raw data, strings, numbers)
    ├── Large Object Space (objects > 256KB)
    ├── Code Space (compiled code)
    └── Map Space (hidden classes)

// 1. Forgotten event listeners
element.addEventListener("click", handler);
// element removed from DOM but handler still references it

// 2. Closures retaining large scopes
function process() {
  const bigData = loadHugeDataset();
  return function summary() {
    return bigData.length; // bigData stays in memory!
  };
}

// 3. Detached DOM trees
const elements = [];
function addElement() {
  const div = document.createElement("div");
  document.body.appendChild(div);
  elements.push(div); // Array keeps reference even after DOM removal
}

// 4. Global variables
function leak() {
  accidental = "I'm global!"; // Missing var/let/const
}