memory-cache-node
A fast and type safe memory cache for Node.js and browser. memory-cache-node
use Javascript Map as cache implementation which
is faster than using Javascript object that some other similar libraries use. memory-cache-node
also uses implementation that does
not block the event loop for a long time, if the cache is very large (hundreds of thousands or millions of entries).
Table of Contents
Installation
npm install --save memory-cache-node
Usage
Creating a memory cache
Below example creates a memory cache for items which has string keys and number values.
Memory cache checks expiring items every 600 seconds (i.e. every 10 minutes)
The maximum number of items in the cache is 1 million.
import { MemoryCache } from 'memory-cache-node';
const itemsExpirationCheckIntervalInSecs = 10 * 60;
const maxItemCount = 1000000;
const memoryCache = new MemoryCache<string, number>(itemsExpirationCheckIntervalInSecs, maxItemCount);
Storing items in the memory cache
Below example stores a permanent item in the memory cache with key key1
and stores an expiring item with key
key2
. The latter item expires earliest after 30 minutes.
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.storePermanentItem('key1', 1);
const timeToLiveInSecs = 30 * 60;
memoryCache.storeExpiringItem('key2', 2, timeToLiveInSecs);
Getting the number of items in the memory cache
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.storePermanentItem('key1', 1);
const timeToLiveInSecs = 30 * 60;
memoryCache.storeExpiringItem('key2', 2, timeToLiveInSecs);
console.log(memoryCache.getItemCount());
Checking if an item exists in the memory cache
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.storePermanentItem('key1', 1);
console.log(memoryCache.hasItem('key1'));
console.log(memoryCache.hasItem('notFound'));
Retrieving the value of an item in the memory cache
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.storePermanentItem('key1', 1);
console.log(memoryCache.retrieveItemValue('key1'));
console.log(memoryCache.retrieveItemValue('notFound'));
Getting the item expiration timestamp
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.storePermanentItem('key1', 1);
console.log(memoryCache.getItemExpirationTimestampInMillisSinceEpoch('key1'));
Removing an item from the memory cache
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.storePermanentItem('key1', 1);
console.log(memoryCache.hasItem('key1'));
memoryCache.removeItem('key1');
console.log(memoryCache.hasItem('key1'));
Clearing the memory cache
Below examples removes all items from the memory cache
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.clear()
Destroying the memory cache
Below example destroys the memory cache and it should not be used after that.
It clears the memory cache and also removes the timer for checking expired items.
NOTE! You should NEVER use a destroyed cache again!
If you try to use a destroyed memory cache, an exception will be thrown.
You should destroy your memory cache if it is not used in your application anymore.
import { MemoryCache } from 'memory-cache-node';
const memoryCache = new MemoryCache<string, number>(600, 1000000);
memoryCache.destroy()
API Documentation
`K` is the type of the item key.
`V` is the type of the item value.
class MemoryCache<K, V> {
constructor(itemsExpirationCheckIntervalInSecs: number, maxItemCount: number);
storePermanentItem(itemKey: K, itemValue: V): void;
storeExpiringItem(itemKey: K, itemValue: V, timeToLiveInSecs: number): void;
getItemCount(): number;
hasItem(itemKey: K): boolean;
getValues(): V[];
getItems(): [K, V][];
retrieveItemValue(itemKey: K): V | undefined;
getItemExpirationTimestampInMillisSinceEpoch(itemKey: K): number | undefined;
removeItem(itemKey: K): void;
exportItemsToJson(): string;
importItemsFrom(json: string): void;
clear(): void;
destroy(): void;
}
License
MIT