Origins and Context
The first web browsers rendered static pages; interactivity was limited to clicking on
links. In 1996, Netscape introduced the first browser with JavaScript (originally known
as ECMAScript), a new scripting language that could be interpreted by the browser while
the page was being viewed.
This doesn’t sound as groundbreaking as it turned out to be, but this enabled web
browsers to evolve from merely passive browsers to dynamic frames for interactive,
networked experiences. This shift ultimately enabled every intra-page interaction we
have on the web today. Without JavaScript, D3 would never exist, and web-based data
visualizations would be limited to pre-rendered, non-interactive GIFs. (Yuck. Thank
you, Netscape!)
Jump ahead to 2005, when Jeffrey Heer (then of the University of California, Berkeley),
Stuart Card (of the Palo Alto Research Center), and James Landay (of the University of
Washington, Seattle) introduced prefuse, a toolkit for bringing data visualization to the
web. prefuse (spelled with all lowercase letters) was written in Java, a compiled language,
whose programs could run in web browsers via a Java plug-in.
Note that Java is a completely different programming language than JavaScript, despite
their similar names. (Hey, it was the 90s, and coffee-related words like “java” were really
cool. Wouldn’t you rather go by “JavaScript” than “ECMAScript”?) Just remember:
JavaScript is a scripting language that is interpreted by the web browser. Java programs
must be compiled and saved as “applets” to be used on the web, and then are executed
by a Java plug-in, not by the browser itself. In practice, this tends to mean that Java
applets stand alone in a little box somewhere within the browser window (much like
Flash Player content). JavaScript, however, is native to the browser, so it can operate
anywhere on the entire page.
Java has now fallen out of favor, in part because its applets are slow to load. Nonetheless,
prefuse was a breakthrough application — the first to make web-based visualization
accessible to less-than-expert programmers. Until prefuse came along, any datavis on
the web was very much a custom affair.
Two years later, in 2007, Jeff Heer introduced Flare, a similar toolkit, but written in
ActionScript, so its visualizations could be viewed on the web through Adobe’s Flash
Player. Flare, like prefuse, relied on a browser plug-in, but the Flash is much faster than
Java ever was — it loads in an instant, and interaction is quick and fluid.
Flare was a huge improvement, but as web browsers continued to evolve, it was clear
that interactive visualizations could be created with native browser technology, no plug-
ins required.
Origins and Context | 9
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