LimitedSet.js

// Harry Kruger
// License: MIT

class LimitedSet extends Set {
    constructor(limit = 0, maxAge = 0, sweepInterval = 1000 * 60, init) {
        super(init);
        this.limit = limit;
        this.maxAge = maxAge;
        this._sweepInterval = sweepInterval;

        this._creationDates = new Map();

        if (this.maxAge && this.sweepInterval) this._createInterval(this.sweepInterval);
    }
    set sweepInterval(val) {
        this._updateInterval(val);
        this._sweepInterval = val;
    }
    get sweepInterval() {
        return this._sweepInterval;
    }
    _createInterval(sweepInterval) {
        this.interval = setInterval(this._sweep.bind(this), sweepInterval);
    }
    _updateInterval(sweepInterval) {
        if (this.interval) {
            this._clearInterval(this.interval);
            this._createInterval(sweepInterval);
        }
    }
    _clearInterval(interval) {
        clearInterval(interval);
    }
    _sweep() {
        for (let value of this.values()) {
            // check if date is older then maxAge
            if (this._creationDates.get(value) + this.maxAge < Date.now()) this.delete(value);
        }
    }
    add(value) {
        // ensure correct limit
        if (this.size && this.limit && this.size >= this.limit) this.delete(this.values().next().value);
        this._creationDates.set(value, Date.now());
        super.add(value);
    }
    delete(value) {
        this._creationDates.delete(value);
        super.delete(value);
    }
    destroy() {
        this._clearInterval(this.interval);
    }
}
module.exports = LimitedSet;