Class fields are the modern way to declare properties on a class. They replace constructor assignments, give you true private fields with #, and provide static members for class-level data. Combined with static initialization blocks, they make class definitions cleaner and more powerful. Key point: Class fields are per-instance by default. #private fields are truly…

JavaScript is garbage-collected — you don’t manage memory manually. But sometimes you need to know when an object is collected, or hold a reference that doesn’t prevent collection. That’s what WeakRef and FinalizationRegistry provide. They’re advanced, rarely needed, and easy to misuse — but essential when the situation calls for them. Key point: WeakRef lets…

The logical assignment operators combine a logical check with assignment. They let you write a ||= b instead of a || (a = b), and the result is shorter, clearer, and avoids double-evaluation of a. Three operators: ||=, &&=, and ??= — each with a specific purpose. Key point: These operators only assign when the…

Optional chaining (?.) lets you safely access deeply nested properties without checking every level. If any link in the chain is null or undefined, the whole expression short-circuits and returns undefined — instead of throwing a TypeError. Key point: ?. short-circuits the entire expression the moment it hits null or undefined. It doesn’t just skip…