how to read ajax fail message code example

Example: ajax error get output

$.ajax({
    type:     "post",
    data:     {id: 0},
    cache:    false,
    url:      "doIt.php",
    dataType: "text",
    error: function (request, error) {
        console.log(arguments);
        alert(" Can't do because: " + error);
    },
    success: function () {
        alert(" Done ! ");
    }
});