clockcache

An easy to use caching mechanism based on the clock cache algorithm.

npm install clockcache
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ClockCache(.js)

ClockCache(.js) an easy-to-use caching mechanism for JavaScript (browser, AMD, and CommonJS/Node) based on the clock page replacement algorithm.

Setup

If you are just loading ClockCache(.js) without a module loader, you can simply directly include the file:

<script src="/path/to/ClockCache.js"></script>
<script>
    var cc = new ClockCache(20);
    cc.fetch = function (key, cb) {
        // implement method for fetching origin data here
    };
</script>

If you are using an AMD module loader you can use the same JavaScript file as an AMD module:

define(['/path/to/ClockCache'], function (ClockCache) {
    var cc = new ClockCache();
    cc.fetch = function (key, cb) {
        // implement method for fetching origin data here
    };
});

If you are using a CommonJS module loader such as the one provided by NodeJS you can use the same JavaScript file as a CommonJS module:

var ClockCache = require('/path/to/ClockCache');
var cc = new ClockCache();
cc.fetch = function (key, cb) {
    // implement method for fetching origin data here
};

If you are specifically using NodeJS and have npm installed then you can simply install ClockCache(.js) as a Node module by executing npm install clockcache. From there you can load the module and use it in your code:

var ClockCache = require('ClockCache');
var cc = new ClockCache();
cc.fetch = function (key, cb) {
    // implement method for fetching origin data here
};

From any of those points you can use cc.get(key, cb) where key is some index you can use to specify the data you want and cb is a callback which takes as arguments data and err where data is the data represented by key and err is false unless there is an error.

The default size of the cache is 20 entries. If you want to change this, simply pass a number to the constructor:

var cc = new ClockCache(100); // cc holds 100 records

You can invalidate an entry by calling cc.invalidate(key). The next time key is passed into get the origin data will be re-fetched.

Example Usage

Consider a case where you are using something like node-request to download the contents of pages. You want to keep a local cache of the content so that you don't have to make repetitive http requests for data which doesn't change too often. You may accomplish this as follows:

var request = require('request'),
    ClockCache = require('clockcache');
var cc = new ClockCache();

cc.fetch = function (key, cb) {
    request({uri: key}, function (error, response, body) {
        cb(body, error);
    });
};

// Now you can request URLs with cc.get('url'):
cc.get('http://google.com', function (data, err) {
    if (!err)
        console.log(data);
    else
        console.error(err);
});

License

The MIT License

Copyright (c) 2012 Kenneth Powers

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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