With this function you can find the total number of users currently signed in to the XBox system. The return value will be an integer value, from 0 - N, where N is the number of signed in users -1.IMPORTANT! This function is only valid when exporting using the UWP target for the Xbox One and it requires you to have checked the Enable XBox Live option in the UWP Game Options.
for(var i = 0; i < xboxlive_get_user_count();
user_id[i] = xboxlive_get_user(i);
The above loops through all the signed in users and stores their unique ID pointer in an array.