fmin is a JavaScript library for unconstrained function minimization that provides several numerical optimization algorithms including Nelder-Mead, Gradient Descent, Wolf Line Search, and Non-Linear Conjugate Gradient methods. It's designed for developers who need to optimize mathematical functions in JavaScript applications, featuring both the core optimization algorithms and interactive D3.js visualizations that demonstrate how these algorithms work. The library is particularly useful for data scientists, machine learning engineers, and developers working on optimization problems who want to implement numerical optimization in their JavaScript projects.