includes

The includes() method checks whether a string contains a specified substring, returning true or false accordingly.

Interactive example

Syntax

Classic signature

function includes<
	GenericInput extends string, 
	GenericSearchString extends string
>(
	input: GenericInput, 
	searchString: GenericSearchString
): input is Extract<GenericInput, `${string}${GenericSearchString}${string}`>;

Curried signature

function includes<
	GenericInput extends string,
	GenericSearchString extends string
>(
	searchString: GenericSearchString
): (
	input: GenericInput
) => input is Extract<GenericInput, `${string}${GenericSearchString}${string}`>;

Parameters

• input: The string in which to perform the search.
• searchString: The substring to search for.

Return value

A boolean indicating whether the substring searchString was found in the string input.

See also

• startsWith: Checks whether a string starts with a specific substring.
• endsWith: Checks whether a string ends with a specific substring.
• indexOf: Returns the index of the first occurrence of a substring.
• lastIndexOf: Returns the index of the last occurrence of a substring.

Sources

• MDN Web Docs: String.prototype.includes()