第一种json结构：
var jsongood =
{"goods":[{"parentId":"null","productId":1,"name":"商品","amount":"null"},{"parentId":1,"productId":11,"name":"水果","amount":"null"}]};
遍历的方法是：
for(var i = 0;i < jsongood.goods.length; i ++){
alert(jsongood.goods[i].amount);}
第二种json结构：
var jsongood =
{"parentId":"null","productId":1,"name":"商品","amount":"null"}
遍历方法：
function getJsonLength(jsonobj){
var length = 0;
for(var i in jsonobj){
length ++;
}
return length;
}
getJsonLength(jsongood)
原文：http://www.cnblogs.com/detanx/p/6290648.html