获取Json对象的长度以及判断json对象是否为空

[{"name":'a',"age":1,"sex":"0","title":"hello","state":"0","id":"1"},{"name":'b',"age":2,"sex":"1","title":"bye","state":"0","id":"2"}]

function getJsonObjLength(jsonObj) {  
    var Length = 0;  
    for (var item in jsonObj) {  
        Length++;  
    }  
    return Length;  
}

alert(getJsonObjLength(str)) //2

var json={a:12,b:45}  
for(var key in json){  
    alert(key);       //a, b  
    alert(json[key]); //12, 45  
}