var tags = ['web', 'yandex', 'JavaScript', 'Yandex', 'script', 'programming'],
module = {},
string="";
module.exports = function (hashtags){
var results = {};
for (i=0; i < hashtags.length; i++) {
results[hashtags[i].toLowerCase()] = 1;
};
result = Object.keys(results);
string = result.join(' ');
};
module.exports(tags);
alert(string);