A performance bottleneck is any part of your code that slows down the entire application.
Even if most of your program is fast, one slow section can make everything feel slow to users.
Finding and fixing bottlenecks is one of the most important skills in performance optimization.
Common Performance Bottlenecks
- Heavy loops running many times
- Repeated DOM updates
- Large data processing in the browser
- Too many event listeners
- Unnecessary API calls
- Memory leaks
Identifying these problems early saves a lot of time later.
Here, the DOM is accessed 1000 times inside a loop.
DOM operations are slow, and repeating them like this creates a serious performance issue.
By storing the element in a variable, we reduce repeated DOM lookups.
This simple change greatly improves performance.
Performance bottlenecks often hide in small sections of code.
By learning to identify slow parts and optimize them, students gain the ability to build fast, responsive, and professional JavaScript applications that perform well in real-world environments.