How to modify JSON object using jquery

How to modify JSON object using jquery

I have  a Json Object n  wanna modify the isVisible property

my testObject  contains below data

"{"id":"1","name":"Apple","isVisible":false}"
"{"id":"2","name":"Orange","isVisible":false}"

I wanna modify isVisible=true

I have tried the below code, but its not working

$(testObject).each( function() {
                  this.isVisible = true;
             
        });