Regression-js: Least Squares Data Fitting

regression-js is a JavaScript module that provides a collection of linear least-squares fitting methods for simple data analysis. It offers capabilities for linear, exponential, logarithmic, power, and polynomial regression. The current stable version is 2.0.1, last published over 8 years ago, suggesting a mature but potentially unmaintained codebase, though it remains widely used. It is a lightweight, pure JavaScript solution that runs both in Node.js and modern browsers. Unlike some broader machine learning libraries, regression-js focuses specifically on classical least-squares curve fitting, providing a straightforward API for common trend analysis tasks without external dependencies.