title: How to find the size of localStorage
body: <p>I am currently developing a site that will make use of HTML5's localStorage. I've read all about the size limitations for different browsers. However, I haven't seen anything on how to find out the current size of a localStorage instance. <a href="https://stackoverflow.com/questions/1248302/javascript-object-size">This question</a> seems to indicate that JavaScript doesn't have a built in way of showing the size for a given variable. Does localStorage have a memory size property that I haven't seen? Is there an easy way to do this that I'm missing?</p>
  
  <p>My site is meant to allow users to enter information in an 'offline' mode, so being able to give them a warning when the storage is almost full is very important. </p>