CODEWITHSUNDEEP
javascripteval
Gautham Renganathan
Gautham Renganathan

Reputation: 645

eval does not work, but JSON.parse does

I have a string returned from the server. It is of the format,

[{"text":"content"}]

where content is a dynamic string and will vary based on user actions. In one such particular case, the returned string cannot be eval'ed, but when I use JSON.parse, it works fine without issues. My eval is like below

eval("(" + response + ")").

Due to certain restrictions I cannot paste the problematic string here. But are there any particular cases where eval will not work and JSON.parse will work?

EDIT1 : I narrowed down the problem and the particular string which gives the problem is,

[{"con" :"g
<\/font><\/td"}]

This string cannot be eval'ed but can by parsed. I guess the issue is because of the sting"/". But I am not able to understand why. Any help in this regard will be great.

EDIT2: There exists an invisible character between g and < and that is causing the issue. Does anyone know what character it is? I will be changing the eval to JSON.parse. But I wanted to know the reason why it failed.

Upvotes: 1

Views: 946

Answers (3)

Bergi
Bergi

Reputation: 664548

That buggy character is U+8232, the Unicode LINE SEPARATOR. It leads to "unterminated string literal" syntax errors in various browsers, this is why it does not work to eval() the string. JSON.parse can work around that, as JSON is not really a JS subset in that perspective.

Upvotes: 2

jw56578
jw56578

Reputation: 399

You are confusing parsing JSON and parsing JavaScript. eval() does not parse JSON. Eval would require valid JS syntax. In "test":"test", the quotes around the property are not valid in javascript object literal notation

Upvotes: -1

raynjamin
raynjamin

Reputation: 788

Use the json2 library to parse your JSON.

Upvotes: 1

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