Javascript JSON.Stringify（）未定义

Question

I am using JSON.Stringify() in my javascript...

var jsonProp;
var json = { };
json.prop= { };
json.prop.Brand = $('.Brand' + val).val();
json.prop.Name = $('.Name' + val).val();
json.prop.Desc = $('.Desc' + val).val();
json.prop.Address = $('.Address' + val).val();
json.prop.Phone = $('.Phone' + val).val();
json.prop.Tag = $('.Tag' + val).val();
json.prop.City = $('.City' + val).val();
json.prop.Status = $('.Status' + val).val();
jsonProp = jsonProp + JSON.stringify(json);

and the result is :

"undefined{"prop":{"Brand":"","Name":"apotik AA","Desc":"","Address":"Address","Phone":"","Tag":"","City":"BEKASI","Status":"0"}}
{"prop":{"Brand":"","Name":"apotik AAaaaa. Bina Farma","Desc":"","Address":"Jl. RA. Kartini, Margahayu-Bekasi Tim., Kota Bks, Jawa Barat 17113","Phone":"","Tag":"","City":"BEKASI","Status":"0"}}"

why is "undefined" there? how can I set it? all I want to have is a JSONArray like this :

Prop{{"Brand":"value","Name":"value"},{"Brand":"value","Name":"value"}}

Please help

Answer 1

Because you declared jsonProp but didn't define it: var jsonProp; . When you don't set a value to a variable, it will be undefined .

Answer 2

When you declare a variable without any unassigned value:

var jsonProp; // default value set to undefined by javascript.

Without any assignment. What javascript does is, it assigns a default value to undefined . That is how it works. So, when you concatenate it:

jsonProp = jsonProp + JSON.stringify(json);
//         undefined + "{prop:{}}"

This happens.

Answer 3

Your variable jsonBiz wasn't defined yet.

So when you do

jsonBiz = jsonBiz + JSON.stringify(json)

You add an undefined value and a string. The first value is turned into the string "undefined", and the two are added.

Answer 4

you need to define jsonBiz before using it.

var jsonBiz = "";

jsonBiz = jsonBiz + JSON.stringify(json);

please try this.