PHP's strrpos in TypeScript

How to use

Install via yarn add locutus and import: import { strrpos } from 'locutus/php/strings/strrpos'.

Or with CommonJS: const { strrpos } = require('locutus/php/strings/strrpos')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	strrpos('Kevin van Zonneveld', 'e')	16
2	strrpos('somepage.com', '.', false)	8
3	strrpos('baa', 'a', 3)	false
4	strrpos('baa', 'a', 2)	2

Here's what our current TypeScript equivalent to PHP's strrpos looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

export function strrpos(haystack: string, needle: string, offset?: boolean | number): number | false {
  //      discuss at: https://locutus.io/php/strrpos/
  // parity verified: PHP 8.3
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //     bugfixed by: Onno Marsman (https://twitter.com/onnomarsman)
  //     bugfixed by: Brett Zamir (https://brett-zamir.me)
  //        input by: saulius
  //       example 1: strrpos('Kevin van Zonneveld', 'e')
  //       returns 1: 16
  //       example 2: strrpos('somepage.com', '.', false)
  //       returns 2: 8
  //       example 3: strrpos('baa', 'a', 3)
  //       returns 3: false
  //       example 4: strrpos('baa', 'a', 2)
  //       returns 4: 2

  let i = -1
  if (typeof offset === 'number') {
    i = (haystack + '').slice(offset).lastIndexOf(needle) // strrpos' offset indicates starting point of range till end,
    // while lastIndexOf's optional 2nd argument indicates ending point of range from the beginning
    if (i !== -1) {
      i += offset
    }
  } else {
    i = (haystack + '').lastIndexOf(needle)
  }
  return i >= 0 ? i : false
}

export function strrpos(haystack, needle, offset) {
  //      discuss at: https://locutus.io/php/strrpos/
  // parity verified: PHP 8.3
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //     bugfixed by: Onno Marsman (https://twitter.com/onnomarsman)
  //     bugfixed by: Brett Zamir (https://brett-zamir.me)
  //        input by: saulius
  //       example 1: strrpos('Kevin van Zonneveld', 'e')
  //       returns 1: 16
  //       example 2: strrpos('somepage.com', '.', false)
  //       returns 2: 8
  //       example 3: strrpos('baa', 'a', 3)
  //       returns 3: false
  //       example 4: strrpos('baa', 'a', 2)
  //       returns 4: 2

  let i = -1
  if (typeof offset === 'number') {
    i = (haystack + '').slice(offset).lastIndexOf(needle) // strrpos' offset indicates starting point of range till end,
    // while lastIndexOf's optional 2nd argument indicates ending point of range from the beginning
    if (i !== -1) {
      i += offset
    }
  } else {
    i = (haystack + '').lastIndexOf(needle)
  }
  return i >= 0 ? i : false
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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