What is LRU caching and how can I implement it in JavaScript?

What is LRU caching and how can I implement it in JavaScript?

LRU stands for Least Recently Used. It's a caching algorithm that removes the least recently used items first. In JavaScript, you can implement it using a combination of a Map and a linked list.

Can you show me a simple implementation of LRU caching in JavaScript?

Sure! Here's a basic implementation:

class LRUCache {
    constructor(limit) {
        this.cache = new Map();
        this.limit = limit;
    }

    get(key) {
        if (!this.cache.has(key)) return -1;
        const value = this.cache.get(key);
        this.cache.delete(key);
        this.cache.set(key, value);
        return value;
    }

    put(key, value) {
        if (this.cache.has(key)) {
            this.cache.delete(key);
        } else if (this.cache.size === this.limit) {
            this.cache.delete(this.cache.keys().next().value);
        }
        this.cache.set(key, value);
    }
}

This class allows you to get and put items while maintaining the LRU order.

How does this implementation handle the limit of cached items?

The implementation checks the size of the cache before adding a new item. If the cache is at its limit, it removes the least recently used item (the first item in the Map) before adding the new one.

What are some use cases for LRU caching?

LRU caching is useful in scenarios like web browsers for storing recently visited pages, database query results, and in-memory data storage for applications to improve performance.