The thesis paper contains a brief introduction to development of modern single-page web applications (SPA) using ReactJS framework and Redux state management library. Single-page applications strive to provide customer experience similar to that found in desktop apps, which is achieved by moving the application logic from the server to the client side of the application. After the initial loading of the webpage, all the following changes are rendered on parts of the page, without the need for a full reload. All the server does is provide needed dana in JSON format. The paper analyses the advantages and disadvantages of this approach to web application development and comes to the conclusion that keeping the application logic on the client-side greatly contributes to the application's responsiveness and user experience as well as server unloading, and is not recommended only for applications that need the initial loading to be very fast. The practical part of the thesis consisted of building the frontend for a single-page application Django Online Judge using ReactJS and Redux, which is described in the paper.