JavaScript Includes
includes() checks whether a string contains a given substring and returns a boolean — true or false. The search is case-sensitive. It is the clean, readable replacement for the old indexOf(...) !== -1 idiom.
Syntax
str.includes(search)Examples
| Input | Arguments | Output |
|---|---|---|
| "hello world" | "world" | true |
| "hello" | "H" | false |
| ↳ Case-sensitive: "H" ≠ "h". | ||
When to use it
- Filter a list by keyword.
- Guard logic on the presence of a marker or flag in text.
Gotchas
- Case-sensitive — lowercase both sides first for a case-insensitive check.
Try it live
Type your input and see Includes transform it instantly.
Want to go further? Chain Includes with other functions in the visual Playground — pipe one output into the next and watch your data transform.