ArrayMap.ts

/**
 *  Key / Value container which enforces a max capacity and
 *  provides several methods for iteration.
 *
 *  Demo:
 *  https://www.typescriptlang.org/play/?target=99#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-iyJlMaBcgzh8DVYkCrpAAD5B4iGdLy7KO9z9ejDUb0dy-QSsbjkePIAHF2ClglQuYspatYMIVtMVgkyDY1h4ki-MWpUvFMrqyoAosQ5ffUiTTiSWTc-WIFCtUvlwYjMbuWTEWSAgdPJUjhCb7dqXeQABkz43W6hj+Qit9Y-x2yhRdwRXECSDXMU7w-fUsA5ZZ2wAhA5kgh9dwWK8VyMElNngnYkPvT9UPQ5cvR9d8Hxg-AiMgB4QJo7JKQjKN3k+RsEy2M4s1iXNIF+IxuBoQNgOI6FYUgHDO27ClHmySNXneKExH0BAm2qdjkyzBpiAlBBTSEiEsMgNRDAORTzGWbg3X7ECDzXCtj2afc-0PSsT347BCjoP4-g7HdmxaVI9JAm8VJaeJWh8r8kCAqinkw6wCHExDJJAkCjLUEylLguhKJSlcSNEqYcty6jOGwUwl2KyERLhCyyqs4q6OXO4WxA-K4TSjLzCktZZOjERBUBDNFgq4TvQKpzbKPKs6HcCQLxUxd4mnP8fK7ZAFha+jpK6JiYz8HTPKzPQCz5QKSxWhDlnuAcbIGFyHJWNCngYmTdpVC9CBwbAGgUNEaj+GhI3IDNFtSTMhqWM7YDasSJru+yZrmryWVBkaUrA9dnDEOCLtw5LioxsVaEkMVWk+wUfsINEAcKMRNtyxK1qQHtajvcgqJh4n2do+nqO2545JjNyPL+cnvt+-61AKTAQf8yBNO01ROOGqHYdxMtJvuhhHPV5yEfcYX6GRvylrR0CyHXPscfV1b8dywmtQAMQFDzAzJr7KepvteZAqjgtxZ33PofVF1LBSlIW-nWuqp2XeDjQeakylgDQABRSRMDEWRh1wQRME+TIHc+9gCFaWhGEgEIwkiGIQSaOhkkvYu9XxOMACIpcoABGNvLi7gAmABmFtm4QVvGw76X+979ou4AVhH3Ux9MCfO8wQeZ4ANgAdgADkXkvx7+SfKDaGeAE4u4ABgPluV+Pte55nruX5Hi3tOJYgZlFpf3C+wFb5j32pgQ6vh34kk-t-Uef8BoAkAUfE+mBN7PyHi2Xwv8kY0wQHTOWWMFT9zQRjD+2Av4-0Pv-OBQA
 *
 */
class ArrayMap<T=any> {

    private maxCapacity: number = 4
    private insertOrder: string[] = []
    private store: Record<string, T> = {}

    public get count(): number {
        return Object.keys(this.store).length
    }

    /**
     * Set the key/value pair and will evict older entries
     * if max capacity is reached. If an eviction occurs 
     * this will also return the evicted value.
     */
    public set(key: string, value: T): T | void {
        this.insertOrder.unshift(key)
        this.store[key] = value
        while (this.count > this.maxCapacity) {
            const expiredKey = this.insertOrder.pop()
            if (expiredKey && expiredKey in this.store) {
                const expiredValue = this.store[expiredKey]
                delete this.store[expiredKey]
                return expiredValue
            }
        }
    }

    public get(key: string): T | undefined {
        return this.store[key]
    }

    public remove(key: string): boolean {
        let didRemove = false
        this.insertOrder = this.insertOrder.filter((storedKey) => {
            if (key === storedKey) {
                delete this.store[key]
                didRemove = true
                return true
            } else {
                return false
            }
        })
        return didRemove
    }

    public all(): T[] {
        return this.insertOrder.map((key) => this.store[key])
    }

    public clear(): void {
        this.store = {}
        this.insertOrder = []
    }

    public map(callback: (input: T) => T): T[] {
        return this.insertOrder.map((key) => {
            const item = this.store[key]
            const next = callback(item)
            this.store[key] = next
            return next
        })
    }

    public filter(callback: (data: T) => boolean): T[] {
        this.insertOrder = this.insertOrder.filter((key) => {
            const value = this.store[key]
            const isFiltered = callback(value)
            
            if (isFiltered) this.remove(key)

            return isFiltered
        })
    }
}

// Example usage

const cache = new ArrayMap<number>()
cache.set("data1", 123)
cache.set("data2", 415)
cache.set("data3", 678)
cache.set("data4", 910)
cache.set("data5", 111)
console.log(cache.all())
cache.clear()
console.log(cache.all())
cache.set("data6", 123)
cache.map((item) => item * 2)
console.log(cache.all())