LRU.js

/**
 * LRU( Least recently used )
 */

import DoubleLinkedList from './DoubleLinkedList';

const LIMIT = 20;

export default class LRUCache {
    constructor(sqList, limit = LIMIT){
        this.limit = limit;
        sqList = (sqList && sqList.length) ? sqList && sqList.slice(0, this.limit) : [];
        this.__cache = new DoubleLinkedList(sqList, function(a, b){
            return a.key === b.key;
        });
    }

    [Symbol.iterator](){
        return this.__cache[Symbol.iterator]();
    }

    get size(){
        return this.__cache.size;
    }
    
    remove(key){
        return this.__cache.remove({ key });
    }

    clear(){
        return this.___cache.clear();
    }
    
    get(key){
        let index = this.__cache.indexOf({ key });

        if(index >= 0) {
            let data = this.__cache.findByIndex(index);
            this.__cache.remove(data);
            this.__cache.unshift(data);

            return data;
        }

        return false;
    }
    
    add(key, value){
        let data = this.get(key);
        if(data) {
            data.value = value;
        } else {
            if(this.size === this.limit) {
                this.__cache.pop();
            }

            this.__cache.unshift({
                key,
                value
            });
        }
    }

    toString(){
        let arr = [];
        this.__cache.forEach(function(data){
            arr.push(`${ data.key }:${ data.value }`);
        });

        return arr.join(' > ');
    }

    toJSON(){
        return this.__cache.toJSON();
    }
}