The lastIndexOf()
method, given one argument: a substring to search for, searches the entire calling string, and returns the index of the last occurrence of the specified substring. Given a second argument: a number, the method returns the last occurrence of the specified substring at an index less than or equal to the specified number.
String.prototype.lastIndexOf()
Try it
Syntax
lastIndexOf(searchString) lastIndexOf(searchString, position)
Parameters
-
searchString
-
Substring to search for.
If the method is called with no arguments,
searchString
is coerced to "undefined
". Therefore,'undefined'.lastIndexOf()
returns0
— because the substringundefined
is found at position0
in the stringundefined
. But'undefine'.lastIndexOf()
, returns-1
— because the substringundefined
is not found in the stringundefine
. -
position
Optional -
The method returns the index of the last occurrence of the specified substring at a position less than or equal to
position
, which defaults to+Infinity
. Ifposition
is greater than the length of the calling string, the method searches the entire string. Ifposition
is less than0
, the behavior is the same as for0
— that is, the method looks for the specified substring only at index0
.-
'hello world hello'.lastIndexOf('world', 4)
returns-1
— because, while the substringworld
does occurs at index6
, that position is not less than or equal to4
. -
'hello world hello'.lastIndexOf('hello', 99)
returns12
— because the last occurrence ofhello
at a position less than or equal to99
is at position12
. -
'hello world hello'.lastIndexOf('hello', 0)
and'hello world hello'.lastIndexOf('hello', -5)
both return0
— because both cause the method to only look forhello
at index0
.
-
Return value
The index of the last occurrence of searchString
found, or -1
if not found.
Description
Strings are zero-indexed: The index of a string's first character is 0
, and the index of a string's last character is the length of the string minus 1.
'canal'.lastIndexOf('a'); // returns 3 'canal'.lastIndexOf('a', 2); // returns 1 'canal'.lastIndexOf('a', 0); // returns -1 'canal'.lastIndexOf('x'); // returns -1 'canal'.lastIndexOf('c', -5); // returns 0 'canal'.lastIndexOf('c', 0); // returns 0 'canal'.lastIndexOf(''); // returns 5 'canal'.lastIndexOf('', 2); // returns 2
Case-sensitivity
The lastIndexOf()
method is case sensitive. For example, the following expression returns -1
:
'Blue Whale, Killer Whale'.lastIndexOf('blue'); // returns -1
Examples
Using indexOf() and lastIndexOf()
The following example uses indexOf()
and lastIndexOf()
to locate values in the string "Brave, Brave New World
".
let anyString = 'Brave, Brave New World'; console.log('The index of the first "Brave" is ' + anyString.indexOf('Brave')); // logs 0 console.log('The index of the last "Brave" is ' + anyString.lastIndexOf('Brave')); // logs 7
Specifications
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
lastIndexOf |
1
|
12
|
1
|
6
|
3
|
1
|
1
|
18
|
4
|
10.1
|
1
|
1.0
|
1.0
|
0.10.0
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf