The topic of this undergraduate thesis is the development of web application which will enable users to easily organize their everyday workout routine. To help users organize their workout routine application offers prefabricated workout plans and individual exercises, as well as possibility of searching through workout plans and exercises. Application also offers users possibility of creating new workout plans and exercises. User can organize plans and exercises, in the form of calendar and daily reports, and they can also track daily activity, calories intake and consumption. JavaScript programming language, React library, Node.JS runtime environment, Express framework and PostgreSql database have been used to develop this application. Important topics have been analyzed while working with React library like difference between class components and function components and correct way of using additional JavaScript libraries and packages, like axios, react-router-dom and react-calendar, inside React. While working with Node.JS runtime environment and Express framework basics of processing HTTP requests and generating HTTP responses, based on data fetched from database, have been studied. Usage of React library and Express server allows the developer to use JavaScript programming language for developing both server and client part of the application. Using same programming language in all parts of the application accelerates and facilitates process of developing an application because it is not necessary to learn two or more programming languages. Also using React library facilitates development of interactive user interface because it lets you compose complex user interfaces from small and isolated pieces of code called components. First part of thesis contains overview of previously mentioned technologies. Second part of thesis contains description of DailyFitness application, its goals and functionalities, basic parts and design.