A JavaScript framework is a pre-written, tried, and tested JavaScript code that developers can use for routine programming tasks instead of rewriting entirely new code. They have become an important aspect of front end web development. These JavaScript frameworks provide a template that developers can use to build a website or web application around. Frameworks often consist of a collection of JavaScript code libraries. Frameworks circumscribe the entire application by providing a structure that keeps code- especially a large codebase- organized. The difference between a JavaScript framework and a library is the control of flow. React, Angular, Vue, and Ember are some examples of popular JavaScript frameworks.