a simple wrapper for localStorage

localStorage Cache Wrapper.js

function cache(key, value, persist, expires){
  if( typeof key == "undefined" ) return;

  var data, is_json,
      cache_value = localStorage.getItem(key);

  // Return value if just the key is passed
  if( typeof value == "undefined" ) {
    // Detect if the string from localStorage tastes like JSON or an Array
    is_json = /^\{|\[.+\}|\]$/.test(cache_value);

    return ( is_json === true ) ? JSON.parse(cache_value): cache_value;
  }

  if( cache_value && persist ) {
    // Stick new value into an array with old value(s)
    data = JSON.parse( cache_value );

    // Don't hold on to more than 5 objects in a key
    if( data.length > 5 ) data.shift();

    if( $.isArray(data) ) {
      data.push(value);
    } else {
      data = [ data, value ];
    }

  } else {
    data = value;
  }

  if( expires ) {
    localStorage.setItem( key + "_expires", ( typeof expires == "number" ) ? expires: Date.now() );
  }

  localStorage.setItem( key, ( typeof value == "object" ) ? JSON.stringify(data): data );
};