JSON对象变化万千，非常灵活，对应的获取方法分别为：
1.最简单类型的（myObject是对象，不是字符串哦）
<script type="text/javascript">
var myObject = {'name':'Kasun', 'address':'columbo','age': '29'}
var count = Object.keys(myObject).length
console.log(count);
</script>
在较老版本的浏览器中需加入以下代码确保可以使用：
if (!Object.keys) {
Object.keys = function (obj) {
var keys = [],
k;
for (k in obj) {
if (Object.prototype.hasOwnProperty.call(obj, k)) {
keys.push(k);
}
}
return keys;
};
}
2.ajax请求返回的值形式：
{"reqStatus":true,"phones":{"one":{"number":"XXXXXXXXXX","type":"mobile"},"two":{"number":"XXXXXXXXXX","type":"mobile"}}}
遍历之：
var key, count = 0;
for(key in data.phones) {
if(data.phones.hasOwnProperty(key)) {
count++;
}
}
3.更多方法*
http://*.com/questions/6756104/get-size-of-json-object
http://*.com/questions/126100/how-to-efficiently-count-the-number-of-keys-properties-of-an-object-in-javascript/4889658#4889658