LRU cache with Map in JavaScript

A fixed-size cache that evicts the least recently used entry, built on Map's insertion order.

class LRUCache {
  constructor(capacity) {
    this.capacity = capacity;
    this.map = new Map();
  }

  get(key) {
    if (!this.map.has(key)) return undefined;
    const value = this.map.get(key);
    this.map.delete(key);
    this.map.set(key, value);
    return value;
  }
}

Keywords and builtins used here

• Map
• class
• const
• constructor
• if
• return
• this

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Step 4 of 4 in Closures, step 4 of 16 in Functions & patterns.

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