Convert circular structure to JSON: Angular2

I have the following object:

someObj = {
  someVar: new FormControl(),
  index: 100,
  array1: [],
  array2: [],
  array3: [],
  array4: []
}

      

        
        
        
      

    

and I am trying to store this in session store. For this I need to use

JSON.stringify(this.someObj);

      

        
        
        
      

    

but I am getting the error:

core.es5.js:1084 ERROR TypeError: Converting circular structure to JSON

      

        
        
        
      

    

After some research, I found that the error was because I have a formControl in my object. Doing something like this

JSON.stringify(this.someObj.searchTerm.value);

      

        
        
        
      

    

will not give an error. But I want to convert the whole object to string representation. I can obviously pass all the individual elements of an object one by one using JSON stringify, but this is not an efficient solution. Can anyone suggest a workaround?