Iteration & Collections

What you'll learn

• The everyday array methods — map, filter, reduce, find, some, every, flatMap, at
• Destructuring and spread for unpacking and combining values
• Optional chaining and nullish coalescing for safe defaults
• The iterator protocol behind for…of, plus generators with yield
• Async iteration for values that arrive over time
• Maps, Sets, and the weak collection family for object-keyed and ephemeral data

1. 01
   Arrays in depth

   The array methods you reach for daily — map, filter, reduce, find, and the rest.
   16 min
2. 02
   Destructuring

   Pulling values out of arrays and objects without the noise.
   14 min
3. 03
   Spread and rest

   Two jobs for one ... — combining values and gathering them.
   13 min
4. 04
   Optional chaining and nullish coalescing

   Reach into uncertain shapes and supply defaults without the && dance.
   14 min
5. 05
   Iterables and for…of

   The protocol that lets a string and an array share the same loop.
   14 min
6. 06
   Generators

   Functions that pause, resume, and produce values lazily.
   14 min
7. 07
   Async iterators and for await…of

   Looping over values that arrive one at a time, over time.
   13 min
8. 08
   Map and Set

   Real key-value collections — for when plain objects start lying to you.
   14 min
9. 09
   WeakMap, WeakSet, WeakRef, FinalizationRegistry

   The weak collection family — small problems each, but they earn their keep.
   18 min