Scanner.md

function Scanner(string) {
    this.string = string;
    this.tail = string;
    this.pos = 0;
}

Scanner.prototype.eos = function () {
    return this.tail === '';
};


Scanner.prototype.scan = function (re) {
    var match = this.tail.match(re);

    if (!match || match.index !== 0) {
        return '';
    }

    var string = match[0];

    this.tail = this.tail.substring(string.length);
    this.pos += string.length;

    return string;
};

Scanner.prototype.scanUntil = function (re) {
    var index = this.tail.search(re),
        match;

    switch (index) {
        case -1:
            match = this.tail;
            this.tail = '';
            break;
        case 0:
            match = '';
            break;
        default:
            match = this.tail.substring(0, index);
            this.tail = this.tail.substring(index);
    }

    this.pos += match.length;

    return match;
};