Javascript JSON.Stringify() what is undefined

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

Why do you write jsonProp = jsonProp + JSON.stringify(json); at all instead of jsonProp = JSON.stringify(json);? — t.niese
– t.niese, Commented Jul 5, 2017 at 7:55
@t.niese because it the content have a grid table and the val is the value of the index of that grid table — Richard
– Richard, Commented Jul 5, 2017 at 10:17

dork · Accepted Answer · 2017-07-05 07:51:21Z

3

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.

answered Jul 5, 2017 at 7:51

dork

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4 Comments

Richard Over a year ago

i declared it as var jsonProp, but still undefined

Ram Over a year ago

@Richard It's still

dork Over a year ago

Like I said, you just declared it but didn't define it. Set a value to it.

Richard Over a year ago

whoa, i undrestand now. Thankyou!

Jai · Accepted Answer · 2017-07-05 07:56:54Z

1

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.

answered Jul 5, 2017 at 7:56

Jai

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Comments

RemcoGerlich · Accepted Answer · 2017-07-05 07:49:43Z

0

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.

answered Jul 5, 2017 at 7:49

RemcoGerlich

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2 Comments

Richard Over a year ago

sorry, i my bad, jsonProp/jsonBiz is var, in my script "var jsonProp;", i edited my question. thankyou

RemcoGerlich Over a year ago

@Richard: yes, but that doesn't change the problem, just imagine my answer also says jsonProp wherever I wrote jsonBiz.

cнŝdk · Accepted Answer · 2017-07-05 07:52:07Z

0

you need to define jsonBiz before using it.

var jsonBiz = "";

jsonBiz = jsonBiz + JSON.stringify(json);

please try this.

edited Jul 5, 2017 at 7:52

cнŝdk

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answered Jul 5, 2017 at 7:50

Rajdeep Agrawal

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