Convert latin digit to persian in vanilla js

toPersianDigit.js

String.prototype.toPersianDigit = function (latinDigit) {
    return this.replace(/\d+/g, function (digit) {
        var enDigitArr = [], peDigitArr = [], i, j;
        for (i = 0; i < digit.length; i += 1) {
            enDigitArr.push(digit.charCodeAt(i));
        }
        for (j = 0; j < enDigitArr.length; j += 1) {
            peDigitArr.push(String.fromCharCode(enDigitArr[j] + ((!!latinDigit && latinDigit === true) ? 1584 : 1728)));
        }
        return peDigitArr.join('');
    });
};

function toPersianDigit(digit) {
  return digit.toString().toPersianDigit();
}