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Add object implementation of FIFO (#4)
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5 files changed

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‎index.js‎

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Original file line numberDiff line numberDiff line change
@@ -1,7 +1,9 @@
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import { fifo } from './src/fifo.js'
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import { lru } from './src/lru.js'
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import { lruObject } from './src/lru-object.js'
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import { fifoObject } from './src/fifo-object.js'
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export { fifo }
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export { lru }
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export { lruObject }
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export { fifoObject }

‎src/fifo-object.js‎

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@@ -0,0 +1,127 @@
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class FIFOObject {
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constructor(max = 0, ttl = 0) {
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this.first = null
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this.items = Object.create(null)
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this.last = null
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this.size = 0
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this.max = max
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this.ttl = ttl
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}
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clear() {
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this.items = Object.create(null)
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this.first = null
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this.last = null
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this.size = 0
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}
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delete(key) {
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if (Object.prototype.hasOwnProperty.call(this.items, key)) {
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const deletedItem = this.items[key]
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delete this.items[key]
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this.size--
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if (deletedItem.prev !== null) {
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deletedItem.prev.next = deletedItem.next
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}
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if (deletedItem.next !== null) {
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deletedItem.next.prev = deletedItem.prev
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}
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if (this.first === deletedItem) {
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this.first = deletedItem.next
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}
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if (this.last === deletedItem) {
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this.last = deletedItem.prev
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}
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}
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}
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evict() {
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if (this.size > 0) {
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const item = this.first
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delete this.items[item.key]
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if (--this.size === 0) {
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this.first = null
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this.last = null
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} else {
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this.first = item.next
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this.first.prev = null
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}
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}
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}
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expiresAt(key) {
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if (Object.prototype.hasOwnProperty.call(this.items, key)) {
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return this.items[key].expiry
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}
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}
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get(key) {
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if (Object.prototype.hasOwnProperty.call(this.items, key)) {
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const item = this.items[key]
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if (this.ttl > 0 && item.expiry <= Date.now()) {
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this.delete(key)
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return
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}
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return item.value
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}
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}
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keys() {
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return Object.keys(this.items)
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}
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set(key, value) {
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// Replace existing item
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if (Object.prototype.hasOwnProperty.call(this.items, key)) {
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const item = this.items[key]
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item.value = value
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item.expiry = this.ttl > 0 ? Date.now() + this.ttl : this.ttl
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return
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}
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// Add new item
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if (this.max > 0 && this.size === this.max) {
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this.evict()
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}
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const item = {
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expiry: this.ttl > 0 ? Date.now() + this.ttl : this.ttl,
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key: key,
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prev: this.last,
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next: null,
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value,
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}
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this.items[key] = item
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if (++this.size === 1) {
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this.first = item
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} else {
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this.last.next = item
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}
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this.last = item
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}
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}
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export function fifoObject(max = 1000, ttl = 0) {
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if (isNaN(max) || max < 0) {
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throw new TypeError('Invalid max value')
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}
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if (isNaN(ttl) || ttl < 0) {
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throw new TypeError('Invalid ttl value')
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}
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return new FIFOObject(max, ttl)
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}

‎src/lru-object.js‎

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Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
class LRU {
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class LRUObject {
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constructor(max = 0, ttl = 0) {
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this.first = null
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this.items = Object.create(null)
@@ -153,5 +153,5 @@ export function lruObject(max = 1000, ttlInMsecs = 0) {
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throw new TypeError('Invalid ttl value')
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}
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return new LRU(max, ttlInMsecs)
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return new LRUObject(max, ttlInMsecs)
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}

‎test/fifo-object.spec.js‎

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import assert from 'node:assert'
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import { it, describe, beforeEach, expect } from 'vitest'
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import { fifoObject } from '../src/fifo-object.js'
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import { items, populateCache } from './utils/cachePopulator.js'
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import { setTimeout } from 'timers/promises'
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describe('FIFO-object', function () {
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let cache
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beforeEach(function () {
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cache = fifoObject(4)
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populateCache(cache)
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})
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describe('constructor validations', () => {
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it('throws on invalid max', () => {
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expect(() => fifoObject('abc')).to.throw(/Invalid max value/)
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})
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it('throws on invalid ttl', () => {
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expect(() => fifoObject(100, 'abc')).to.throw(/Invalid ttl value/)
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})
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})
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describe('clear', () => {
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it('Clear whole cache', () => {
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expect(Array.from(cache.keys())).toHaveLength(4)
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cache.clear()
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expect(Array.from(cache.keys())).toHaveLength(0)
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})
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})
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describe('evict', () => {
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it('It should evict', function () {
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expect(cache.first.key).toBe('b')
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expect(cache.last.key).toBe('e')
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expect(cache.size).toBe(4)
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cache.evict()
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expect(cache.first.key).toBe('c')
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})
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it('does not crash when evicting from empty cache', () => {
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cache.clear()
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expect(Array.from(cache.keys())).toHaveLength(0)
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cache.evict()
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expect(Array.from(cache.keys())).toHaveLength(0)
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})
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it('adjusts links to null when evicting last entry', () => {
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cache = fifoObject(4)
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cache.set(items[0], items[0])
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expect(Array.from(cache.keys())).toHaveLength(1)
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expect(cache.last.value).toBe(items[0])
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expect(cache.first.value).toBe(items[0])
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cache.evict()
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expect(Array.from(cache.keys())).toHaveLength(0)
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expect(cache.last).toBeNull()
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expect(cache.first).toBeNull()
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})
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})
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describe('get', () => {
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it('deletes expired entries', async () => {
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cache = fifoObject(4, 500)
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populateCache(cache)
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await setTimeout(300)
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cache.set(items[2], items[2])
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const item1Pre = cache.get(items[1])
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const item2Pre = cache.get(items[2])
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await setTimeout(300)
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const item1Post = cache.get(items[1])
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const item2Post = cache.get(items[2])
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expect(item1Pre).toBe(false)
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expect(item1Post).toBeUndefined()
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expect(item2Pre).toBe(items[2])
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expect(item2Post).toBe(items[2])
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})
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})
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describe('set', () => {
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it('Does not set expiration time on resetting entry when ttl is 0', () => {
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cache = fifoObject(1000, 0)
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cache.set(items[0], false)
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cache.set(items[0], items[0])
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expect(cache.expiresAt(items[0])).toBe(0)
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})
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})
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describe('delete', () => {
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it('It should delete', function () {
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assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.size, 4, "Should be '4'")
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assert.strictEqual(cache.items['e'].next, null, "Should be 'null'")
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assert.strictEqual(cache.items['e'].prev.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['d'].next.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.items['d'].prev.key, 'c', "Should be 'c'")
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assert.strictEqual(cache.items['c'].next.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['c'].prev.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.items['b'].next.key, 'c', "Should be 'c'")
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assert.strictEqual(cache.items['b'].prev, null, "Should be 'null'")
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cache.delete('c')
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assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.size, 3, "Should be '3'")
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assert.strictEqual(cache.items['e'].next, null, "Should be 'null'")
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assert.strictEqual(cache.items['e'].prev.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['d'].next.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.items['d'].prev.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.items['b'].next.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['b'].prev, null, "Should be 'null'")
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cache.delete('e')
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assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.size, 2, "Should be '2'")
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cache.get('b')
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assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.first.prev, null, "Should be 'null'")
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assert.strictEqual(cache.first.next.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.last.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.last.prev.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.next, null, "Should be 'null'")
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assert.strictEqual(cache.size, 2, "Should be '2'")
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})
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it('Adjusts first item after it is deleted', () => {
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expect(cache.first.key).toBe('b')
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expect(cache.last.key).toBe('e')
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expect(cache.size).toBe(4)
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cache.delete(cache.first.key)
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expect(cache.first.key).toBe('c')
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expect(cache.last.key).toBe('e')
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expect(cache.size).toBe(3)
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})
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})
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describe('core', () => {
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it('It should handle a small evict', function () {
150+
assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.size, 4, "Should be '4'")
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assert.strictEqual(cache.items['e'].next, null, "Should be 'null'")
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assert.strictEqual(cache.items['e'].prev.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['d'].next.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.items['d'].prev.key, 'c', "Should be 'c'")
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assert.strictEqual(cache.items['c'].next.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['c'].prev.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.items['b'].next.key, 'c', "Should be 'c'")
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assert.strictEqual(cache.items['b'].prev, null, "Should be 'null'")
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cache.delete('c')
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assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.size, 3, "Should be '3'")
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assert.strictEqual(cache.items['e'].next, null, "Should be 'null'")
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assert.strictEqual(cache.items['e'].prev.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['d'].next.key, 'e', "Should be 'e'")
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assert.strictEqual(cache.items['d'].prev.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.items['b'].next.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.items['b'].prev, null, "Should be 'null'")
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cache.delete('e')
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assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.size, 2, "Should be '2'")
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cache.get('b')
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assert.strictEqual(cache.first.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.first.prev, null, "Should be 'null'")
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assert.strictEqual(cache.first.next.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.last.key, 'd', "Should be 'd'")
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assert.strictEqual(cache.last.prev.key, 'b', "Should be 'b'")
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assert.strictEqual(cache.last.next, null, "Should be 'null'")
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assert.strictEqual(cache.size, 2, "Should be '2'")
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})
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it('It should handle an empty evict', function () {
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cache = fifoObject(1)
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assert.strictEqual(cache.first, null, "Should be 'null'")
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assert.strictEqual(cache.last, null, "Should be 'null'")
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assert.strictEqual(cache.size, 0, "Should be 'null'")
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cache.evict()
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assert.strictEqual(cache.first, null, "Should be 'null'")
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assert.strictEqual(cache.last, null, "Should be 'null'")
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assert.strictEqual(cache.size, 0, "Should be 'null'")
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})
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it('It should expose expiration time', function () {
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cache = fifoObject(1, 6e4)
198+
cache.set(items[0], false)
199+
assert.strictEqual(typeof cache.expiresAt(items[0]), 'number', 'Should be a number')
200+
assert.strictEqual(cache.expiresAt('invalid'), undefined, 'Should be undefined')
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})
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it('It should reset the TTL after resetting value', async () => {
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cache = fifoObject(1, 100)
205+
cache.set(items[0], false)
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const n1 = cache.expiresAt(items[0])
207+
assert.strictEqual(typeof n1, 'number', 'Should be a number')
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assert.strictEqual(n1 > 0, true, 'Should be greater than zero')
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await setTimeout(50)
210+
211+
cache.set(items[0], false)
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const n2 = cache.expiresAt(items[0])
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assert.strictEqual(typeof n2, 'number', 'Should be a number')
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assert.strictEqual(n2 > 0, true, 'Should be greater than zero')
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assert.strictEqual(n2 > n1, true, 'Should be greater than first expiration timestamp')
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})
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})
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})

‎toad-cache.d.ts‎

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Original file line numberDiff line numberDiff line change
@@ -3,6 +3,9 @@ export function lruObject<T = any>(max?: number, ttl?: number): ToadCache<T>;
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export function lru<T = any>(max?: number, ttl?: number): ToadCache<T>;
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55
export function fifo<T = any>(max?: number, ttl?: number): ToadCache<T>;
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7+
export function fifoObject<T = any>(max?: number, ttl?: number): ToadCache<T>;
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69
export interface ToadCache<T> {
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first: T | null;
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last: T | null;

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