JSFiddle - React, Tailwind, and code Playground

JavaScript

var obj = {"name" : "one", "test" : [{"random1" : true},{"random2" :  false}] };

console.log("obj at the beginning:");
console.log(obj);

$.extend( true,
         obj, 
        {"name" : "one", "test" : [{"random2" :  true}]}
        );

$.extend( true,
         obj,
         {"name" : "one", "test" : [{"random18" : true}] }
        );         
obj.test = obj.test[0];

console.log("obj after second extension:");
console.log( obj );