JavaScript frameworks provide developers with pre-written code for common programming patterns, abstracting away tedious tasks involved in setting up and running an application, allowing developers to focus on building features of their applications. The terms library and framework are often used interchangeably but a framework acts as a foundation with which developers can build and design their applications, while a library consists of pre-written code snippets or functions that provide specific functionality. Modern JavaScript frameworks such as React, Node.js, Angular, Vue.js, and Ember.js offer various features and trade-offs, and developers need to consider these carefully when deciding which one is most suitable for their application's needs. Each framework has its own strengths and weaknesses, and understanding the differences between them can help developers choose the best fit for their project.