JavaScriptCore is a powerful engine that executes JavaScript code, primarily used in web browsers and applications. It was developed by Apple for their WebKit framework, which powers the Safari browser. This engine allows developers to run scripts, manipulate web pages, and create dynamic content, making it essential for modern web development. One of the key features of JavaScriptCore is its ability to optimize code for better performance. It includes a Just-In-Time (JIT) compiler that translates JavaScript into machine code, allowing for faster execution. This makes it a popular choice for developers looking to enhance the speed and efficiency of their web applications.