Cannot get the length of JSON array in javascript

Question

I have read other issues regarding accessing a json array in javascript, but nothing helped in my case. I am receiving the below json in jquery ajax call.

{"jList":"[{\"added_by\":\"Ani\",\"description\":\"example description.\",\"start_date
\":\"2014-10-10\",\"mark\":255,\"id\":975},{\"added_by\":\"Ani\",\"description
\":\"example description..\",\"start_date\":\"2014-10-10\",\"mark\":255,\"id\":980
}]"}

receiving method-

$.getJSON("url",
                {var : Val},
                function(data){
                    here...

All I want is to count the JSON objects in this array. In the above case I want an length output as 2 but I'm not getting it. I have tried below things-

data.jList.length -- < giving 200 like something as output
Object.keys(data).length -- < giving 200 like something as output
Object.keys(data['jList']).length -- < giving 1 as output

How do I get 2 as length output of the above array?

Can you add your controller code here? So it will good if we set it from code-behind. — Mehmood
– Mehmood, Commented Aug 8, 2015 at 22:07
Open your developer console (F12 in most browsers) and use console.log(theVariable); to see what it contains. — Sverri M. Olsen
– Sverri M. Olsen, Commented Aug 8, 2015 at 22:21

Jan · Accepted Answer · 2015-08-08 22:00:41Z

2

The jList property of the object is just a string, so you need to convert it to a Javascript object using JSON.parse().

// Dummy of your "data" variable
var data = {"jList":"[{\"added_by\":\"Ani\",\"description\":\"example description.\",\"start_date \":\"2014-10-10\",\"mark\":255,\"id\":975},{\"added_by\":\"Ani\",\"description \":\"example description..\",\"start_date\":\"2014-10-10\",\"mark\":255,\"id\":980 }]"};

var myList = JSON.parse(data.jList);
alert(myList.length); // Alerts "2"

edited Aug 8, 2015 at 22:00

answered Aug 8, 2015 at 21:55

Jan

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2 Comments

user3378974 Over a year ago

what do we do by parsing the data here? i have explicitly defined in the controller that the return datatype should be json.

Jan Over a year ago

@user3378974 Your return type IS JSON. Just so happens that whatever method is producing the JSON is sending the jList property as a string. That's a server-side issue, not client-side. If your return type wasn't JSON, you wouldn't be able to do data.jList, it would return undefined.

Amit · Accepted Answer · 2015-08-08 21:53:54Z

0

"jList":"[{\"added_by\":\"... is not an array, it's a string (and that's why it's length is 456 or 200 if you change the question).

Remove the surrounding double-quotation marks for it to be an array. Then you'll have Array.prototype.length.

answered Aug 8, 2015 at 21:53

Amit

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1 Comment

Amit Over a year ago

Thanks -1. Any reason?

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