Web browsers have scaled from simple page-rendering engines to operating systems that include most services the lower OS layer has, with the added facility that applications can be run by just visiting a web page. In this paper we will describe the front and back end of a distributed evolutionary computation system that uses the browser's capabilities of running programs written in JavaScript. We will focus on two different aspects of volunteer computing: first, the pragmatic: where to find those resources, which ones can be used, what kind of support you have to give them; and then, the theoretical: how evolutionary algorithms can be adapted to an environment in which nodes come and go, have different computing capabilities and operate in complete asynchrony of each other. We will examine the setup needed to create a simple distributed evolutionary algorithm using JavaScript, with the intention of eventually finding a model of how users react to it by collecting data from several experiments featuring a classical benchmark function.