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

Prompt

Write complete, highly optimized pure JavaScript code (for the Three.js environment) that procedurally creates an infinite, rich 3D world including islands, ocean, rivers, streams, dense forests, and detailed sprawling distinct cities (including large cities and villages situated in deserts, large cities and villages situated on the coast, and cities and villages situated along rivers, etc.), very large urban infrastructure, mountains, glaciers, deserts, road traffic (including a huge variety of cars, buses, trains, trams, etc.), air traffic (including helicopters, airplanes, etc.), with playable exploration controls, dynamic chunking, and zero external assets or placeholders. Just give me the JS code, not a full HTML file, start writing code from <script>.