Я бы предложил этот код
window.cookie = {
set: function(c_name, value, exdays, path = '/') {
var exdate = new Date();
exdate.setDate(exdate.getDate() + exdays);
var c_value = escape(value) + ((exdays == null) ? "" : ("; expires=" + exdate.toUTCString())) + "; path=" + path;
document.cookie = c_name + "=" + c_value;
},
get: function(c_name) {
var i, x, y, ARRcookies = document.cookie.split(";");
for (i = 0; i < ARRcookies.length; i++) {
x = ARRcookies[i].substr(0, ARRcookies[i].indexOf("="));
y = ARRcookies[i].substr(ARRcookies[i].indexOf("=") + 1);
x = x.replace(/^\s+|\s+$/g, "");
if (x == c_name) {
return unescape(y);
}
}
}
};
И вы можете проверить так:
if("undefined" !== typeof cookie.get('lang')){
//cookie is not set
cookie.set('lang', 'en', 1);
}else{
//cookie is set
}