JavaScript Interview Prep: Arrays, Sets, Maps and Big O With Real Code Examples

A tutorial series on JavaScript and TypeScript interview concepts has released its second installment, focusing on data structures and algorithm fundamentals. The article explains the practical differences between Arrays, Sets, and Maps, emphasizing that each structure answers a different kind of question about data. Real-world examples include using a Set to detect duplicate emails during a bulk CSV import and using a Map for fast key-based lookups instead of repeated array scans. The piece also introduces Big O notation as a way to understand how code performance scales with input size, rather than measuring raw speed. Unlike typical whiteboard exercises, the examples are drawn from production scenarios such as bulk row selection and contact importing features.