var RE_UCHARS = /([\uD800-\uDBFF][\uDC00-\uDFFFF]|[\S\s])/g;
var codepoints = function (string) {
    return string.replace(RE_UCHARS, '_').length;
};
var substring = function (string, length) {
    return string.match(RE_UCHARS).slice(0, length).join('');
};
var just = function (append) {
    return function (string, length, chars) {
        var str, len, chr, diff, fill = '';
        if (typeof this === 'string' || this instanceof String) {
            str = this;
            len = string;
            chr = length ? length : ' ';
        }
        else {
            str = string;
            len = length;
            chr = chars ? chars : ' ';
        }
        diff = len - codepoints(str);
        if (diff <= 0) {
            return str;
        }
        do {
            fill += chr;
        } while (diff > codepoints(fill));
        fill = substring(fill, diff);
        return append ? str + fill : fill + str;
    };
};
var ljust = just(true);
var rjust = just(false);
var install = function () {
    String.prototype['ljust'] = ljust;
    String.prototype['rjust'] = rjust;
};
install.ljust = ljust;
install.rjust = rjust;
module.exports = install;