javascript push json object to array

Question

I have the following:

var cookie = $.cookie("Test_cookie");
var items = cookie ? eval("([" + cookie + "])") : [];
var jsonObj = { packageId: "11", machineId: "1", operationType: "Download" };
items.push(jsonObj);
$.cookie(cookieName, JSON.stringify(items), { expires: 1, path: '/' });

result:

[{"packageId":"11","machineId":"1","operationType":"Download"}]

which is correct.

However, when I run it the second time I want to append new object to items but json gets messed up (notice extra "["):

var jsonObj = { packageId: "11", machineId: "1", operationType: "Download" };
items.push(jsonObj);
$.cookie(cookieName, JSON.stringify(items), { expires: 1, path: '/' });

result:

[[{"packageId":"11","machineId":"1","operationType":"Download"}],{"packageId":"11","machineId":"1","operationType":"Download"}]

and it should be:

[{"packageId":"11","machineId":"1","operationType":"Download"},{"packageId":"11","machineId":"1","operationType":"Download"}]

what gives?

Some servers will alert you monthly by email - for suspicious scripts in your pages. Thanks to eval() — Roko C. Buljan
– Roko C. Buljan, Commented Feb 28, 2013 at 14:23
@roXon - They should charge you monthly as well, for using eval! — adeneo
– adeneo, Commented Feb 28, 2013 at 14:24
@adeneo :D :D :D hahahahahah now I need another coffee ;) YMMD — Roko C. Buljan
– Roko C. Buljan, Commented Feb 28, 2013 at 14:27

JoDev · Accepted Answer · 2013-02-28 14:23:55Z

3

Your mistake is near

var items = cookie ? eval("([" + cookie + "])") : [];

Just do

var items = cookie ? eval(cookie) : [];

answered Feb 28, 2013 at 14:23

JoDev

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10 Comments

ShaneKm Over a year ago

that did it!. thank you! I will accept your answer in 9 min :)

Roko C. Buljan Over a year ago

in that case the eval is quite unneeded (and dangerous tho) specially if used in combinations with cookies ;)

David Hedlund Over a year ago

JSON.parse would be preferred over eval.

Roko C. Buljan Over a year ago

@JoelDuret now that you pointed it out I see I'm wrong, but in any case.... eval is not that evil if used smartly, but there's other ways to "evaluate" a string. There's always a way. using eval() is any attacker's dream and is sign of poor scripting

ShaneKm Over a year ago

Joel, how would I pop from a list of json objects?

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