Which component is responsible for executing JavaScript programs in a web browser?

The component responsible for executing JavaScript programs in a web browser is the interpreter. JavaScript is a high-level, interpreted programming language, which means that the code is executed on-the-fly by the interpreter present in the web browser rather than being compiled into machine code prior to execution.

When a web page containing JavaScript is loaded, the browser's JavaScript engine interprets the code line by line at runtime, allowing the browser to execute the scripts dynamically. This feature is what enables interactive content on web pages, such as handling user inputs, updating the UI, and making asynchronous requests without refreshing the entire page.

In contrast, a compiler transforms the entire source code of a program into machine code in one go before it is executed, which is not how JavaScript operates within browsers. Similarly, a debugger is a tool used for testing and debugging code rather than executing it, and an assembler is used to convert assembly language into machine code, which is unrelated to the execution of JavaScript. Thus, the role of the interpreter is crucial in facilitating the real-time execution of JavaScript code in the browser environment.