JavaScript (ES2026) reference · String Methods

JavaScript String lastIndexOf() Method

Return the index of the last occurrence of some text, searching backwards, or -1 if it isn't found.

JavaScript (ES2026) Since ES1

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Syntax

string.lastIndexOf(searchString, position)

Parameter	Description
`searchString`	Text to look for.
`position` optional	Search backwards from this index.

An index, or -1.

File name from a pathTry it yourself

const path = "/home/ada/notes.txt";
console.log(path.slice(path.lastIndexOf("/") + 1));

Output

notes.txt

Last match or -1Try it yourself

console.log("a.b.c".lastIndexOf("."), "abc".lastIndexOf("z"));

Output

3 -1

Version	Change
JavaScript ES1	Added

string.indexOf() · Return the index of the first occurrence of some text, or -1 if it isn't found.
string.slice() · Extract part of a string between two indexes; negative indexes count from the end.
JavaScript Strings · tutorial
JavaScript String Methods · tutorial