PHP's chr in TypeScript

How to use

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

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

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	chr(75) === 'K'	true

Notes

• Unlike PHP (which wraps at 256), this implementation supports Unicode code points beyond 255 using surrogates

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

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

export function chr(codePt: number): string {
  //      discuss at: https://locutus.io/php/chr/
  // parity verified: PHP 8.3
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Brett Zamir (https://brett-zamir.me)
  //          note 1: Unlike PHP (which wraps at 256), this implementation
  //          note 1: supports Unicode code points beyond 255 using surrogates
  //       example 1: chr(75) === 'K'
  //       returns 1: true

  if (codePt > 0xffff) {
    // Create a four-byte string (length 2) since this code point is high
    //   enough for the UTF-16 encoding (JavaScript internal use), to
    //   require representation with two surrogates (reserved non-characters
    //   used for building other characters; the first is "high" and the next "low")
    codePt -= 0x10000
    return String.fromCharCode(0xd800 + (codePt >> 10), 0xdc00 + (codePt & 0x3ff))
  }
  return String.fromCharCode(codePt)
}

export function chr(codePt) {
  //      discuss at: https://locutus.io/php/chr/
  // parity verified: PHP 8.3
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Brett Zamir (https://brett-zamir.me)
  //          note 1: Unlike PHP (which wraps at 256), this implementation
  //          note 1: supports Unicode code points beyond 255 using surrogates
  //       example 1: chr(75) === 'K'
  //       returns 1: true

  if (codePt > 0xffff) {
    // Create a four-byte string (length 2) since this code point is high
    //   enough for the UTF-16 encoding (JavaScript internal use), to
    //   require representation with two surrogates (reserved non-characters
    //   used for building other characters; the first is "high" and the next "low")
    codePt -= 0x10000
    return String.fromCharCode(0xd800 + (codePt >> 10), 0xdc00 + (codePt & 0x3ff))
  }
  return String.fromCharCode(codePt)
}

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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