未捕获的TypeError：无法读取属性JSON

Question

I have JSON PHP Output below

{"data_0":{"data_1":{"A":0,"B":0},"data_2":{"C_C":"CC","D_D":"DD"}}}

In jQuery have code :

$.ajax({
    url : 'process.php',
    dateType: 'json',
    type: 'POST',
    data : {val : data_val},
    success: function(data){
        $(data.data_0.data_2).each(function(key, value) {
        alert(key + " " + value);
        });

But when run I received error : Uncaught TypeError: Cannot read property 'data_2' of undefined.

How to fix it ?

Thanks you so much.