Turn a sequence of numbers into a sequence of words

lookSaySequence.js

var lookSaySequence = (function() {

    var words = {
        '0': 'zero',
        '1': 'one',
        '2': 'two',
        '3': 'three',
        '4': 'four',
        '5': 'five',
        '6': 'six',
        '7': 'seven',
        '8': 'eight',
        '9': 'nine'
    };
    
    var re = new RegExp('0123456789'.split('').join('+|') + '+', 'g');
    
    return function(num) {
        if (typeof num === 'undefined') return;
        
        num = ''+num;
        
        var arry = num.match(re);
        
        var result = arry.map(function(n) {
            var end = n.length === 1 ? '' : 's';
            return words[n.length] + ' ' + words[n.charAt(0)] + end;
        });
        
        if (result.length === 1) return result[0];
        if (result.length === 2) return result[0] + ' and ' + result[1];
        
        return  result.slice(0, result.length - 1).join(', ') + ', and ' + result.slice(-1);
    }
}());