json access data not showing properly

Question

I'm currently processing some json encoded data, but I can't access it properly, this are some tests I did:

Code fragment 1:

var json = [
{"MarkerId":1,"0":1,"UserId":2147483647,"1":2147483647,"locX":51,"2":51,"LocY":4,"3":4},
{"MarkerId":2,"0":2,"UserId":2147483647,"1":2147483647,"locX":55,"2":55,"LocY":4,"3":4}];
console.log(json[0][0]);

outputs:

1

Code fragment 2:

var json2 = getCookie('markers');
console.log(json2[0][0]);

outputs:

[

Code fragment 3:

console.log(getCookie('markers'));

output:

[{"MarkerId":1,"0":1,"UserId":2147483647,"1":2147483647,"locX":51,"2":51,"LocY":4,"3":4},{"MarkerId":2,"0":2,"UserId":2147483647,"1":2147483647,"locX":55,"2":55,"LocY":4,"3":4}]

as you can see when I use the result from test 3 hardcoded I can access it fine, but when I use it only in code i get something diffrent

does anyone know how to do this?

ThiefMaster · Accepted Answer · 2013-12-05 18:12:06Z

5

Cookies only store strings. You need to use JSON.parse() to convert them back to an object. Also, the contents of json isn't JSON but a JAvaScript object (actually, an array).

var obj2 = JSON.parse(getCookie('markers') || '[]');
console.log(obj2[0][0]);

The || '[]' falls back to an empty array if the cookie is missing since an empty string or undefined wouldn't be valid JSON.

answered Dec 5, 2013 at 18:12

ThiefMaster

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2 Comments

rab Over a year ago

([])[0][0] will gives TypeError: Cannot read property '0' of undefined

ThiefMaster Over a year ago

True, in the example it'll fail. But in his actual code he probably won't just blindly access that element.

rab · Accepted Answer · 2013-12-05 18:13:34Z

1

The getCookie('markers') returns string. The native javascript method JSON.parse(text[, reviver]) , parse a string as JSON.

 var json2 = getCookie('markers');
 if ( typeof(json2 ) == "string" ) {
      json2 = JSON.parse( json2 );  
 }

Then try your code ..

answered Dec 5, 2013 at 18:13

rab

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2 Comments

rlemon Over a year ago

When would you expect the cookie not to be a string? Wouldn't it make more sense to handle empty cookies for this value in a more transparent way?

rab Over a year ago

@rlemon I know that .. but in question there less informtion about getCookie method . Thanks for pointing out that

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