includes(): finding text and understanding case sensitivity

Useful to know

String.includes() returns true or false according to whether a sequence is present in the text. The check distinguishes uppercase and lowercase letters. It is not a search by meaning and does not mean matching only a whole word. [1]

For example, 'Book catalog'.includes('Book') is true, and the same search text for 'BOOK' gives false. If you want case-insensitive matching, you can also normalize the text and query according to the needs of the language.

It is also important what you consider to be an empty request. Searching for an empty string returns true, so the interface must separately decide whether the empty field means "show everything" or "enter search".

For a small list in the browser includes() may be sufficient. For searching with grammatical forms, arrangement by relevance or a lot of data, an additional solution is needed. Don't introduce simple character finding as a full-fledged search engine.