What did you study about the browser engine work?

The browser engine consists of several key components:

• JavaScript engine — responsible for parsing and executing JS code. For example, V8 in Chrome, SpiderMonkey in Firefox. It compiles JS into machine code and optimizes execution.

• Rendering engine (layout engine) — responsible for parsing HTML and CSS, building DOM and CSSOM, computing styles, layout (placing elements), and rendering the page. Examples include Blink in Chrome, Gecko in Firefox.

• Networking layer — handles HTTP requests, resource loading (HTML, CSS, JS, images).

• Security — includes same-origin policy, sandboxing, CORS, protection against XSS and other attacks.

The engine's work begins with loading HTML, building DOM, while CSS and JS load in parallel. After DOM and CSSOM are built, layout and paint occur. The JS engine can influence the DOM, so sometimes a re-layout occurs.

An example of a simplified lifecycle:

1. Load HTML ->
2. Build DOM ->
3. Load and parse CSS ->
4. Build CSSOM ->
5. JS executes, possibly changing DOM ->
6. Layout (calculate sizes and positions) ->
7. Paint (rendering) ->
8. Composite (assemble layers for display)

Optimization techniques such as minimizing reflow and repaint, lazy loading, caching, and asynchronous resource loading are also studied.