simple-mem-cache

A simple in-memory cache for node.js. By Fabio Rotondo.

Installation

yarn add simple-mem-cache

or

npm install simple-mem-cache --save

Usage

var smc = require ( 'simple-mem-cache' );

// now just use the cache
smc.add ( 'hello', 'world' );

// add an item that expires after 6 seconds
smc.add ( 'expiring', 'in 6 seconds', 6000 );

// add an item that when expires calls a cback
smc.add ( 'boom', 'exploding', 3000, ( key, val ) => {
    console.log ( 'KA-BOOOM for k: %s - v: %s', key, val );
} );

// Get values
console.log ( 'Hello: ', smc.get ( 'hello' ) );
console.log ( 'expiring: ', smc.get ( 'expiring' ) );
console.log ( 'boom: ', smc.get ( 'boom' ) );

which should print

Hello:  world
expiring:  in 6 seconds
boom:  exploding

and after 6 seconds, also:

KA-BOOOM for k: boom - v: exploding

You can obtain the full items collection with:

// Get current items as JSON string
const s = smc.stringify ();

And also add elements to the cache by parsing a previously JSON dump:

// Adding elements from a previously JSON dump
smc.parse ( s );

With the skipExisting flag, you will not override elements in the memory cache:

// Adding elements from a previously JSON dump skipping keys already present
smc.parse ( s, true );

API

add ( key, value, expire, expireCallback )

Stores a value in the cache. You can automatically remove the given value from the cache providing the expire attribute (a numeric value indicating the duration time of the value expressed in milliseconds). Also, optionally, if the value is going to expire, you can specify an expireation callback to be called at that time.

Parameters:

• key: the cache key name for retrieving value

• value: the cache value. Can be any JavaScript type.

• expire: the value duration time in memory (in milliseconds). If omitted, the key will last forever.

• expireCallback: the callback to be called when the item expires from cache. It will be called with the following signature:

  expireCallback ( key, value )

Returns

This method returns the value just cached.

get ( key, defaultValue )

Retrieves the value for the specified key. If the key is not found in the cache, defaultValue is returned.

Parameters:

• key: the cache key name
• defaultValue: (optional) the value to be returned if key is missed.

Returns

This method returns the value in cache or defaultValue.

del ( key )

Deletes the provided key from the cache.

Parameters:

• key: the cache key name

Returns

This method returns nothing.

clear ()

Completely swipe cache data from memory.

Returns

This method returns nothing.

stringify ()

Returns a string rappresentation of key/values in memory.

Returns

Returns a JSON string rappresenting the current key/values in memory.

parse ( json, skipExisting )

Restore keys / values inside the json string into memory cache. If skipExisting is true, keys already present in the memory cache are preserved.

Parameters

• json: The JSON string to be parsed.
• skipExisting: (optional) If set to true keys already present in the memory cache are preserved.

keys ()

Returns all the keys currently in cache.

size

This is a class read only property that returns the numeber of keys in the cache.

hits

This is a class read only property that returns the number of cache hits.

misses

This is a class read only property that returns the number of cache misses for statistic purposes.

Changelog

0.2.0: TypeScript Edition

• Rewritten in TypeScript
• Moved from jest to mocha/chai

0.1.3: Added jest tests