dynamic tokens in offer throwing an error

Hey guys,

I am trying to access the customer attributes directly into offer as referred in this Post.

Following is the code snippet that I have used.

var a = "${crs.personalized experience.blog page visitors}"
console.log('offer ran!')

console.log(a)

When this block executes error is thrown in with status 500

Network call - status: 500, message: "An error has occurred while processing your request, please try again later"

Is this causing because of the white spaces in attribute name? or I have missed something. 
I am new to Target, pls point me to right documentation or share your thoughts.