Underscore.js is a JavaScript utility library that provides a set of helpful functions for performing common programming tasks in a more concise and expressive way. It enhances the functionality of JavaScript by extending the native object prototypes and providing additional utility functions.
With Underscore.js, developers can easily manipulate arrays, objects, and collections. It offers functions for iterating and transforming data, filtering and sorting arrays, and performing mathematical operations. It also provides utility functions for handling functions, templates, and asynchronous operations.