This paper introduces p5.spatial.js, an open source JavaScript library for creating multichannel sound works in the web browser. Designed to extend the popular creative coding environment p5.js, p5.spatial.js adds multichan- nel audio output support to the popular, interactive, artist- friendly toolkit. p5.spatial.js is also compatible with existing community-made examples, many of which include stylized motion, or particle systems, that can be readily adapted to animate the trajectory of sound sources in spatial audio contexts. The library implements Distance-Based Amplitude Panning (DBAP), a technique used for irregular speaker configurations typically found in art installation and perfor- mance environments. It supports quadraphonic, octophonic, and 5.1 surround setups, and can be modified to address custom loudspeaker arrays via a user-defined JSON object. Designed to be accessible to a community of artists and designers who use p5.js, the library serves non-specialists and experienced composers of computer music alike.