String.prototype.lastIndexOf() - JavaScript | MDN

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coerced to strings

Substring to search for. All values are coerced to strings, so omitting it or passing undefined causes lastIndexOf() to search for the string "undefined", which is rarely what you want.

Using indexOf() and lastIndexOf()

The following example uses indexOf() and lastIndexOf() to locate values in the string "Brave, Brave New World".

String.prototype.charAt()

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Array.prototype.indexOf()

Array.prototype.lastIndexOf()

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This page was last modified on Oct 1, 2025 by MDN contributors.

toLocaleLowerCase()

toLocaleUpperCase()

[Symbol.iterator]()

[Symbol.hasInstance]()

__defineGetter__()

__defineSetter__()

__lookupGetter__()

__lookupSetter__()

propertyIsEnumerable()