$.ajax({

  url: 'https://randomuser.me/api/',

  dataType: 'json',

  success: function(data){

    var user = data.results[0].user,

        list = $('.form-control'),

        prop;

​

    for (var i = 0, len = list.length; i < len; i += 1) {

      prop = user[ $(list[i]).attr('id') ];

      if ( prop ) $(list[i]).val(prop);

    }

  }

});