Weeks 6-8: Advanced Arrays, Problem-Solving Patterns, and Building a Data CLI

Three Weeks of Backend Fundamentals: Arrays, Patterns, and Building a Real Tool Weeks 6 through 8 were a turning point. Not because the content was the hardest so far, but because it was the first time everything started connecting. Arrays, performance, patterns, Node.js. Here's what those three weeks looked like. Week 6: Advanced Array Methods + Big O This week was about using array methods on realistic data, not just [1, 2, 3] examples. Working with product data meant chaining methods together to answer real questions — total value of in-stock items, most expensive item per category, filtering by rating and price simultaneously. The one that clicked hardest was reduce for grouping: const grouped = products.reduce((acc, p) => { if (!acc[p.category]) acc[p.category] = []; acc[p.category].push(p); return acc; }, {}); Once you understand this pattern, you see it everywhere. Big O in Plain Terms The Big O section was kept practical, not academic. The number that stuck: Processing 1,000 it