Write complete, highly optimized pure JavaScript code (for a...

Prompt

Write complete, highly optimized pure JavaScript code (for a Three.js environment) that procedurally generates an infinite, rich 3D world seamlessly featuring islands, dense forests, and detailed sprawling cities, huge infrastructures, mountains, glaciers, road traffic (including variety of cars, buses, trains, trams. etc.) with playable exploration controls, dynamic chunking, and zero external assets or placeholders. Give me only JS code, not complete HTML file.