Checking if strings contain specific substrings is fundamental for search functionality, data validation, content filtering, and implementing features like autocomplete or keyword highlighting in JavaScript applications. As the creator of CoreUI, I’ve implemented substring checking extensively in components like search bars, filter systems, and validation logic where detecting specific text patterns is crucial for user experience. From my extensive expertise, the most modern and intuitive solution is using the ES6 includes() method, which returns a clear boolean result. This approach is readable, performant, and specifically designed for substring detection with excellent browser support.