lastIndexOf

The lastIndexOf() method returns the index of the last occurrence of a substring in a string, or undefined if the substring is not found.

Interactive example

Syntax

Classic signature

function lastIndexOf<
	GenericInput extends string
>(
	input: GenericInput, 
	searchString: string, 
	position?: number
): number | undefined;

Curried signature

function lastIndexOf<
	GenericInput extends string
>(
	searchString: string
): (input: GenericInput) => number | undefined;

Parameters

• input: The string in which to search.
• searchString: The substring to search for.
• position (optional): The position in the string from which to start searching backward. By default, the search starts at the end of the string.

Return value

The index of the last occurrence of the substring, or undefined if the substring is not found.

See also

• match: Retrieves matches of a string against a regular expression.
• endsWith: Checks whether a string ends with a specific substring.
• includes: Checks whether a string contains a substring.

Sources

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