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replaceBeforeLast

Replace the substring before the last occurrence of a specified search string.

Usage

import replaceBeforeLast from 'https://cdn.jsdelivr.net/gh/stdlib-js/string-base-replace-before-last@esm/index.mjs';

replaceBeforeLast( str, search, replacement, fromIndex )

Replaces the substring before the last occurrence of a specified search string.

var str = 'beep boop';
var out = replaceBeforeLast( str, ' ', 'loop', str.length );
// returns 'loop boop'

out = replaceBeforeLast( str, 'o', 'bar', str.length );
// returns 'barop'

To begin searching from a specific index, provide a corresponding fromIndex argument.

var out = replaceBeforeLast( 'beep boop beep', ' ', 'loop', 5 );
// returns 'loop boop beep'

If fromIndex is less than zero, the starting index is resolved relative to the last string character, with the last string character corresponding to fromIndex = -1.

var out = replaceBeforeLast( 'beep boop beep', ' ', 'loop', -1 );
// returns 'loop beep'

Notes

If a search string is not present in a provided string, the function returns the provided string unchanged.
If a search string is an empty string, the function returns the provided string unchanged.
If fromIndex resolves to an index which is less than 0, the function returns the provided string unchanged.

Examples

<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">

import replaceBeforeLast from 'https://cdn.jsdelivr.net/gh/stdlib-js/string-base-replace-before-last@esm/index.mjs';

var str = 'beep boop';
var out = replaceBeforeLast( str, 'p', 'see', str.length );
// returns 'seep'

str = 'Hello World!';
out = replaceBeforeLast( str, 'xyz', 'foo', str.length );
// returns 'Hello World!'

str = 'Hello World!';
out = replaceBeforeLast( str, '', 'foo', str.length );
// returns 'Hello World!'

str = '';
out = replaceBeforeLast( str, 'xyz', 'foo', str.length );
// returns ''

</script>
</body>
</html>

See Also

@stdlib/string-base/replace-after-last: replace the substring after the last occurrence of a specified search string.
@stdlib/string-base/replace-after: replace the substring after the first occurrence of a specified search string.
@stdlib/string-base/replace-before: replace the substring before the first occurrence of a specified search string.

Notice

This package is part of stdlib, a standard library with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2025. The Stdlib Authors.

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