How to use the iconv-lite.encodingExists function in iconv-lite

// Hack to make iconv load the encodings module, otherwise jest crashes. Compare
// https://github.com/sidorares/node-mysql2/issues/489
require('iconv-lite').encodingExists('cesu8');

// load dotenv
require('dotenv').config();

function getSupportedEncoding (encoding) {
  if (encoding === 'ISO-8859-8-I') encoding = 'ISO-8859-8'
  if (iconv.encodingExists(encoding)) return encoding
  return 'utf8' // default
}

function _getCharset(str, isMeta) {
  var charset;
  if ((isMeta ? META_CHARSET_RE : CHARSET_RE).test(str)) {
    charset = RegExp.$1;
    if (!iconv.encodingExists(charset)) {
      charset = null;
    }
  }

  return charset;
}

function _getCharset(str, isMeta) {
	var charset;
	if ((isMeta ? META_CHARSET_RE : CHARSET_RE).test(str)) {
		charset = RegExp.$1;
		if (!iconv.encodingExists(charset)) {
			charset = null;
		}
	}
	
	return charset;
}

if(err){
                    cb(err);
                }else if(!bodyContent){
                    cb(null,result);
                }else{
                    var record      = doc[0],
                        resHeader   = record['resHeader'] || {};
                    try{
                        var headerStr    = JSON.stringify(resHeader),
                            charsetMatch = headerStr.match(/charset="?([a-zA-Z0-9\-]+)"?/),
                            imageMatch   = resHeader && resHeader["content-type"];

                        if(charsetMatch && charsetMatch.length){

                            var currentCharset = charsetMatch[1].toLowerCase();
                            if(currentCharset != "utf-8" && iconv.encodingExists(currentCharset)){
                                bodyContent = iconv.decode(bodyContent, currentCharset);
                            }
                            result.type    = "text";
                            result.content = bodyContent.toString();
                        }else if(imageMatch && /image/i.test(imageMatch)){

                            result.type    = "image";
                            result.mime    = imageMatch;
                            result.content = bodyContent;
                        }else{
                            result.content = bodyContent.toString();
                        }
                    }catch(e){}

                    cb(null,result);
                }

function autoDecodeCharset(data){
    if(data){
        var buffer = new Buffer(data),
            charset = chardet.detect(buffer);
        console.log(('Data charset is '+charset ).magenta.bold);
        try {
            data = buffer.toString(charset);
          } catch (e) {
            if(Iconv.encodingExists(charset)){
                data = Iconv.decode(buffer,charset);
            }
          }
        return data;
    }
}//end autoDecodeCharset
/**

export function encode(string, encoding = 'utf8') {
  if (encoding === 'utf8') return Buffer.from(string, 'utf8')

  if (!iconv.encodingExists(encoding))
    throw new Error(`Encoding does not exist: "${encoding}"`)

  return iconv.encode(string, encoding)
}

function normalizeCharset(charset) {
    charset = charset
        && charset.replace(/[- ]/g, "").toLowerCase()
        || "utf8";

    assert.ok(
        iconv.encodingExists(charset),
        "Unrecognized charset: " + charset
    );

    return charset;
}

function decode(content, encoding) {
    if (encoding !== 'UTF-8') {
        logger.Debug('Decoding with: ' + encoding);
        var iconv = require('iconv-lite');
        if(iconv.encodingExists(encoding))
            var buffer = iconv.decode(content, encoding);
        else if (iconv.encodingExists(encoding.replace('CP', 'win')))
            var buffer = iconv.decode(content, encoding.replace('CP', 'win'));
        else
            buffer = content;
    } else {
        buffer = content
    }
    return buffer.toString('UTF-8');
};

function _parser(filename) {
        var fileBuffer = grunt.file.read(filename, {
          encoding: null
        });
        var detected = jschardet.detect(fileBuffer);
        var fileContent;

        if (iconv.encodingExists(detected.encoding)) {
          fileContent = iconv.decode(fileBuffer, detected.encoding);
          grunt.log.debug(filename + ' - encoding detected: ' + detected.encoding);
        } else {
          fileContent = iconv.decode(fileBuffer, 'utf8');
          grunt.log.debug(filename + ' - encoding not detected, used utf-8 instead');
        }

        csv.parse(fileContent, options, function(error, output) {
          if (error) {
            _cb(error);
          } else {
            lines = lines.concat(output);
            _cb();
          }
        });
      }