text: module.exports = function htmlspecialchars (string, quoteStyle, charset, doubleEncode) {
    //       discuss at: https://locutus.io/php/htmlspecialchars/
    //      original by: Mirek Slugen
    //      improved by: Kevin van Zonneveld (https://kvz.io)
    //      bugfixed by: Nathan
    //      bugfixed by: Arno
    //      bugfixed by: Brett Zamir (https://brett-zamir.me)
    //      bugfixed by: Brett Zamir (https://brett-zamir.me)
    //       revised by: Kevin van Zonneveld (https://kvz.io)
    //         input by: Ratheous
    //         input by: Mailfaker (https://www.weedem.fr/)
    //         input by: felix
    // reimplemented by: Brett Zamir (https://brett-zamir.me)
    //           note 1: charset argument not supported
    //        example 1: htmlspecialchars("<a href='test'>Test</a>", 'ENT_QUOTES')
    //        returns 1: '&lt;a href=&#039;test&#039;&gt;Test&lt;/a&gt;'
    //        example 2: htmlspecialchars("ab\"c'd", ['ENT_NOQUOTES', 'ENT_QUOTES'])
    //        returns 2: 'ab"c&#039;d'
    //        example 3: htmlspecialchars('my "&entity;" is still here', null, null, false)
    //        returns 3: 'my &quot;&entity;&quot; is still here'
  
    let optTemp = 0
    let i = 0
    let noquotes = false
    if (typeof quoteStyle === 'undefined' || quoteStyle === null) {
      quoteStyle = 2
    }
    string = string || ''
    string = string.toString()
  
    if (doubleEncode !== false) {
      // Put this first to avoid double-encoding
      string = string.replace(/&/g, '&amp;')
    }
  
    string = string
      .replace(/</g, '&lt;')
      .replace(/>/g, '&gt;')
  
    const OPTS = {
      ENT_NOQUOTES: 0,
      ENT_HTML_QUOTE_SINGLE: 1,
      ENT_HTML_QUOTE_DOUBLE: 2,
      ENT_COMPAT: 2,
      ENT_QUOTES: 3,
      ENT_IGNORE: 4
    }
    if (quoteStyle === 0) {
      noquotes = true
    }
    if (typeof quoteStyle !== 'number') {
      // Allow for a single string or an array of string flags
      quoteStyle = [].concat(quoteStyle)
      for (i = 0; i < quoteStyle.length; i++) {
        // Resolve string input to bitwise e.g. 'ENT_IGNORE' becomes 4
        if (OPTS[quoteStyle[i]] === 0) {
          noquotes = true
        } else if (OPTS[quoteStyle[i]]) {
          optTemp = optTemp | OPTS[quoteStyle[i]]
        }
      }
      quoteStyle = optTemp
    }
    if (quoteStyle & OPTS.ENT_HTML_QUOTE_SINGLE) {
      string = string.replace(/'/g, '&#039;')
    }
    if (!noquotes) {
      string = string.replace(/"/g, '&quot;')
    }
  
    return string
  }
  