try not to use es6 in front end

[Walidmash]

es6 is not supported in all browsers, so prevent using it in your front end code https://github.com/facg3/msn-AutoComplete/blob/8c372d2136eec1a1ef9a7ffdb6da271cd51ef2f3/public/dom.js#L38

[Salam-Dalloul]

done!