@newdash/newdash/functional/LRUMap.js

javascript/typescript utility library

"use strict";
// ref: https://stackoverflow.com/a/46432113/4380476
// Author: odinho - Velmont
Object.defineProperty(exports, "__esModule", { value: true });
exports.LRUMap = void 0;
const assert_1 = require("../assert");
const errors_1 = require("../assert/errors");
/**
 * LRU (Least Recently Used) Map implementation
 */
class LRUMap extends Map {
    /**
     * the max number of total items
     */
    _maxSize;
    /**
     * LRU (Least Recently Used) Map implementation
     *
     * will remove the oldest item when reach the size limit
     *
     * @category Functional
     * @since 5.15.0
     * @param maxSize maximum cache item number, default is 1024
     * @example
     *
     * ```ts
     * const m = new LRUMap(1)
     * m.set('a','v') // {'a':'v'}
     * m.set('b','c') // {'b':'c'}
     * ```
     */
    constructor(maxSize = 1024) {
        super();
        (0, assert_1.mustProvide)(maxSize, "maxSize", "number");
        if (maxSize < 1) {
            throw new errors_1.InValidParameterError(`for LRUMap, must provide a positive value which >=1, giving ${maxSize}`);
        }
        this._maxSize = maxSize;
    }
    get(key) {
        if (super.has(key)) {
            const item = super.get(key);
            // refresh key
            super.delete(key);
            super.set(key, item);
        }
        return super.get(key);
    }
    set(key, val) {
        // refresh key
        if (super.has(key)) {
            super.delete(key);
        }
        // evict oldest
        else if (this.size >= this._maxSize) {
            super.delete(this.first());
        }
        super.set(key, val);
        return this;
    }
    clear() {
        super.clear();
    }
    first() {
        return super.keys().next().value;
    }
    setMaxSize(maxSize) {
        this._maxSize = maxSize;
    }
    getMaxSize() {
        return this._maxSize;
    }
}
exports.LRUMap = LRUMap;
exports.default = LRUMap;