PHP's quoted_printable_encode in JavaScript

How to use

You you can install via yarn add locutus and require this function via const quoted_printable_encode = require('locutus/php/strings/quoted_printable_encode').

It is important to use a bundler that supports tree-shaking so that you only ship the functions that you actually use to your browser, instead of all of Locutus, which is massive. Examples are: Parcel, webpack, or rollup.js. For server-side use this is typically less of a concern.

Examples

Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#	code	expected result
1	quoted_printable_encode('a=b=c')	'a=3Db=3Dc'
2	quoted_printable_encode('abc \r\n123 \r\n')	'abc =20\r\n123 =20\r\n'
3	quoted_printable_encode('0123456789012345678901234567890123456789012345678901234567890123456789012345')	'012345678901234567890123456789012345678901234567890123456789012345678901234=\r\n5'

Here’s what our current JavaScript equivalent to PHP's quoted_printable_encode looks like.

module.exports = function quoted_printable_encode(str) {
  //  discuss at: https://locutus.io/php/quoted_printable_encode/
  // original by: Theriault (https://github.com/Theriault)
  // improved by: Brett Zamir (https://brett-zamir.me)
  // improved by: Theriault (https://github.com/Theriault)
  //   example 1: quoted_printable_encode('a=b=c')
  //   returns 1: 'a=3Db=3Dc'
  //   example 2: quoted_printable_encode('abc   \r\n123   \r\n')
  //   returns 2: 'abc  =20\r\n123  =20\r\n'
  //   example 3: quoted_printable_encode('0123456789012345678901234567890123456789012345678901234567890123456789012345')
  //   returns 3: '012345678901234567890123456789012345678901234567890123456789012345678901234=\r\n5'
  //        test: skip-2

  const hexChars = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F']
  const RFC2045Encode1IN = / \r\n|\r\n|[^!-<>-~ ]/gm
  const RFC2045Encode1OUT = function (sMatch) {
    // Encode space before CRLF sequence to prevent spaces from being stripped
    // Keep hard line breaks intact; CRLF sequences
    if (sMatch.length > 1) {
      return sMatch.replace(' ', '=20')
    }
    // Encode matching character
    const chr = sMatch.charCodeAt(0)
    return '=' + hexChars[(chr >>> 4) & 15] + hexChars[chr & 15]
  }

  // Split lines to 75 characters; the reason it's 75 and not 76 is because softline breaks are
  // preceeded by an equal sign; which would be the 76th character. However, if the last line/string
  // was exactly 76 characters, then a softline would not be needed. PHP currently softbreaks
  // anyway; so this function replicates PHP.

  const RFC2045Encode2IN = /.{1,72}(?!\r\n)[^=]{0,3}/g
  const RFC2045Encode2OUT = function (sMatch) {
    if (sMatch.substr(sMatch.length - 2) === '\r\n') {
      return sMatch
    }
    return sMatch + '=\r\n'
  }

  str = str.replace(RFC2045Encode1IN, RFC2045Encode1OUT).replace(RFC2045Encode2IN, RFC2045Encode2OUT)

  // Strip last softline break
  return str.substr(0, str.length - 3)
}

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we assimilate first iterations with imperfections, hoping for others to take issue with-and improve them. This unorthodox approach has worked very well to foster fun and fruitful collaboration, but please be reminded to use our creations at your own risk. THE SOFTWARE IS PROVIDED "AS IS" has never been more true than for Locutus.

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