Memory leaks in JavaScript can significantly impact an application's performance, leading to slowdowns, crashes, and high latency. These issues often arise due to misunderstandings about automatic memory management in high-level languages like JavaScript. Memory leaks occur when memory that is no longer needed is not returned to the operating system, often due to logical flaws rather than invalid code. Key causes include global variables, closures, detached DOM elements, timers, event listeners, and caches. To manage memory effectively, understanding memory cycles and garbage collection algorithms, such as reference counting and mark-and-sweep, is crucial. Developers are encouraged to use tools like Chrome DevTools to identify and resolve memory leaks, and to adopt good coding practices, such as careful use of global variables and closures, to prevent memory leaks from affecting application performance.