0Pricing
JavaScript Academy · Lesson

Iteration Patterns

Iterate Map and Set with for...of; use entries/keys/values; convert to arrays; build tiny counters and unique lists.

Iteration overview

Goal: Learn simple, clear iteration.

  • Map: entries, keys, values
  • Set: values
  • Convert to arrays
  • Frequency counter & unique lists
Iteration Patterns — illustration 1

Map: entries/keys/values

Use for...of on a Map to get [key, value]; keys() and values() are also available.

// Map iterates as [key, value] pairs
const prices = new Map();
prices.set("apple", 3);
prices.set("banana", 2);

for (const [item, cost] of prices) {
  console.log(item, cost);
}

// You can also use keys() or values()
for (const k of prices.keys()) {
  console.log("key:", k);
}
for (const v of prices.values()) {
  console.log("value:", v);
}
Iteration Patterns — illustration 2

All lessons in this course

  1. Map & Set essentials
  2. WeakMap & WeakSet — simple privacy and caches
  3. Iteration Patterns
← Back to JavaScript Academy