ba-whatevcache.js

/*!
 * JavaScript whatevCache - v0.2pre - 12/30/2010
 * http://benalman.com/
 *
 * Copyright (c) 2010 "Cowboy" Ben Alman
 * Dual licensed under the MIT and GPL licenses.
 * http://benalman.com/about/license/
 */

// whatevCache.set( key, value [, ttl ] );
// (returns undefined on success, error object otherwise)
//
// whatevCache.get( key );
//
// whatevCache.remove( key );

var whatevCache = function(){

  var global = this,
      cache = {},
      undef,

      // "Borrowed" from Modernizr
      use_localStorage = global.JSON && function(){
        try {
          return ( 'localStorage' in global ) && global.localStorage !== null;
        } catch ( e ) {
          return false;
        }
      }();

  // Expose these methods.
  return {
    set: set,
    get: get,
    remove: remove
  };

  // Set a key-value pair with optional TTL.
  function set( key, value, ttl ) {
    var expires = ttl && new Date( +new Date() + ttl * 1000 ),
        obj = {
          expires: +expires,
          value: value
        };

    if ( use_localStorage ) {
      try {
        localStorage[ key ] = JSON.stringify( obj );
      } catch ( e ) {
        return e;
      }
    } else {
      cache[ key ] = obj;
    }
  }

  // Get a value if it exists and hasn't expired.
  function get( key ) {
    var obj,
        val;

    if ( use_localStorage ) {
      obj = localStorage[ key ];
      if ( obj ) {
        obj = JSON.parse( obj );
      }
    } else {
      obj = cache[ key ];
    }

    if ( obj ) {
      if ( obj.expires && obj.expires < +new Date() ) {
        remove( key );
      } else {
        val = obj.value;
      }
    }

    return val;
  }

  // Remove a key-value pair.
  function remove( key ) {
    if ( use_localStorage ) {
      localStorage.removeItem( key );
    } else {
      delete cache[ key ];
    }
  }

}();