如何使用JavaScript遍历属性以获得具有相同值的计数或长度?

I have the following object, Please let me know how to iterate over this object to get the count/length of the property(category) value to know how many times it is repeated.

喜欢:

FIRST is repeated one-time(i.e count or length: 1)
    SECOND is repeated three times(i.e count or length: 3)
    THIRD is repeated three times(i.e count or length: 3)
    FOURTH is repeated one-time (i.e count or length: 1)

var categorycount =

    [{"name":"ABC","vals":[{"description":"first description","category":"FIRST"},
    {"description":"second description","category":"SECOND"},
    {"description":"third description","category":"SECOND"},
    {"description":"fourth description","category":"SECOND"},
    {"description":"fifth description","category":"THIRD"},
    {"description":"sixth description","category":"THIRD"}, 
    {"description":"eighth description","category":"THIRD"},
    {"description":"ninth description","category":"FOURTH"},

    ]}];
    var obj = JSON.stringify(categorycount[0].vals);
    console.log(obj);

jsfiddle.