DEV Community 👩‍💻👨‍💻

Sandeep kamboj
Sandeep kamboj

Posted on

Parse JSON string without JSON.parse and eval()


    var jsonStr="{name:'abc',age:20}";
    var jsonObject = (new Function( "return " + jsonStr ) )() ;
    console.log(jsonObject);

Enter fullscreen mode Exit fullscreen mode

Top comments (4)

Collapse
 
fnh profile image
Fabian Holzer

JSON.parse would yield a syntax error in this example, because jsonStr is not acutally JSON, since JSON requires double quotes for string, and requires the keys to be in string form as well.

But what is much more grave, this function is prone to script injection.

let jsonObject = 
  (letsHopeItsJson) => ((new Function( "return " + letsHopeItsJson) )())

let iffe = "(function(){alert('script injection')})()";

console.log(jsonObject(iffe));


`

Collapse
 
sandeepkamboj12 profile image
Sandeep kamboj

yes. this code is also used for script injection.

I have checked jquery parseJSON method in jquery library in 1.x version. It also uses this technique to parse json..

Collapse
 
fnh profile image
Fabian Holzer • Edited on

Just to be perfectly clear: script injection is not a feature, it is a security vurnerabilty. And that jQuery, in an apparently rather old version, did this in its days, is no excuse to repeat the mistake in 2018.

Thread Thread
 
glauberfunez profile image
Glauber Funez

right and what would be the best way to do that since JSON.parse doesn't work because it has a function?
I ask that because I have a very similar scenario.

👀 Just want to lurk?

That's fine, you can still create an account and turn on features like 🌚 dark mode.