locutus/esm/php/strings/quoted_printable_encode.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export function quoted_printable_encode(str) {
    //      discuss at: https://locutus.io/php/quoted_printable_encode/
    // parity verified: PHP 8.3
    //     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'
    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.endsWith('\r\n')) {
            return sMatch;
        }
        return sMatch + '=\r\n';
    };
    str = str.replace(RFC2045Encode1IN, RFC2045Encode1OUT).replace(RFC2045Encode2IN, RFC2045Encode2OUT);
    // Strip last softline break (only if it's a soft break =\r\n, not a hard break \r\n)
    if (str.endsWith('=\r\n')) {
        return str.slice(0, -3);
    }
    return str;
}