91-DIVOC-02: Local Storage

April 5, 2020 > 91-DIVOC-02: "COVID-19 Data for Locations of People You Love"

A lot of people had amazing suggestions on the COVID-19 visualization and I implemented many of them to make the visualization as useful to as many people as possible. One specific suggestion -- to allow the visualization to "remember" your previous choice -- was added with a quick bit of code to use a cookie to remember your previously selected county and state.

Even though this feature was added nearly two weeks ago, I was never entirely happy with it. Specifically, when a cookie is used, all of the data stored in the cookie is sent to the server every time a page is loaded. For this site, that is absolutely not needed -- the highlighting of a selected country on the COVID-19 visualization is done inside of your web browser and not by the server. I was certain there was a way to do this better: How can I store user settings without needing to send the data to the server?

The goal of my second 91-DIVOC project was to explore the storage options available for "remembering" user preferences without a database. I found that every modern browser supports three ways:

So localStorage is the winner -- a large amount of data can be stored, the data is private (never sent to the server), and persists for a long time. But how can I build something to explore this technology?

Reflecting on the past week, I found myself caring less and less on the depressing global statistics and focusing more on the cases and deaths in the communities where I have people I love. The University of Illinois is located in Champaign County, Illinois and, as April 5, 2020, the cases have started to explode -- 400% growth, from 11 to 55 cases, all in the past week.

My second project was to create a COVID-19 tool that shows only the data from the locations that means the most to you:

COVID-19 Data for Locations of People You Love >>

If you have never created something that has had user preferences saved locally -- not without a database or other infrastructure -- this was surprisingly easy. It's worth getting it a shot and I hope you go start creating! :)