Tuesday, March 11, 2014

Tools for HTML Table and Browser-Side Database Manipulation

I've been having a lot of fun building a realistic-looking demo app that is meant to showcase the features of a coming product. A big challenge in such cases is obviously dynamic data, since hard-coded data won't cut it. It needs to behave like a web app, providing the illusion of a server-side database, but without a server-side database.

HTML5 provides built-in client-side persistence features called sessionStorage and localStorage, but when the data requirements are complex, as in my application, these just aren't adequate. What I need is a client-side database like SQLite. As it turns out, different browsers have taken different routes to providing client-side databases, and it made my head hurt to read about Web SQL and SQLite and which browser incorporated which database and which browser abandoned which database. Finally, I found a JavaScript library called HTML5SQL.js that promised to abstract all those implementation issues from me, giving me a standard API to work with.

So far, it's worked great for me and seems very powerful and flexible. So that's the first tool I'd recommend, for client-side database manipulation - HTML5SQL.js.

Then I had the challenge of building HTML tables that would display this data, allow the user to manipulate it visually and save changes. After a lot of searching, I found another nice JavaScript library called DataTables. DataTables provides lots of powerful features, including sortable columns and pagination. These work even in the default settings with no configuration.

So that's the second tool I'd recommend, for HTML table manipulation - DataTables.js.

By blending HTML5SQL and DataTables functions, I could create HTML tables from a client-side  database. Even better, I could open multiple tabs on the browser, each representing a different part of the application, and they could all see the same data, because the database is a global resource to all tabs in the browser. Best of all, the data stayed persistent across browser restarts. It's a true database, with persistence, relational structure and SQL smarts.

Other tools:

Needless to say, jQuery has now become required technology, and a web developer simply cannot leave home without it. It's so powerful I'm still looking for the right categorisation to describe it.

Many of the new JavaScript libraries are built in an asynchronous style, so a rather naive usage assuming synchronous behaviour (that a function invoked first will complete before the next invoked function) will lead to some surprises. If you need to ensure that two asynchronous functions are executed in strict sequence, you will need to resort to callbacks, as explained on StackOverflow.

For visual designers, the old method of using HTML tables to lay out components is now passé. Using CSS layouts is the in thing. A popular CSS layout framework is called the "960 Grid System", or 960.gs. It's named for the fact that most modern screens have a width of at least 960 pixels, and this number lends itself to being divided into 12 or 16 columns with spaces or gutters in-between. A newer one is unsemantic, which is said to be better for "responsive" UIs (those that adapt to different screen sizes, such as desktop browsers, tablets and mobile phones), but is a bit more complex to use. In both these frameworks, HTML components such as "div" and "table" elements just need to be given special class names, and the CSS then uses these to lay them out. It's quite neat and powerful, but I'm not working in that area because I'm not a graphic or layout designer. I've just seen the nice effects you can get with a CSS layout framework.