A JISON developer designs and implements parsing algorithms using the JISON parsing system. They utilize this JavaScript-based tool to create parsers for programming languages, data formats, or structured text. They ensure the correct syntax and semantics of a language are accurately translated into a format that a computer can understand. They also debug and optimize the parsers to improve performance and efficiency. Furthermore, they may also contribute to the improvement of JISON itself, adding new features or fixing bugs. A JISON developer's role is crucial in software development, particularly in compiler construction and language design.