function add(a, b, output) { output.out = a + b; } var output = {}; add(5, 3, output); console.log(output); //output: {out: 8}
function func(obj) { obj = JSON.parse(JSON.stringify(obj)); //If too slow, replace with other method of deep cloning obj.a += 10; return obj.a; } var myObj = {a: 5}; func(myObj); //Returns 15 and myObj.a is still 5