Arrays and Objects In Prototypes - Not Treated as References

Question

I have a prototype object in Javascript, when I initialise a new instance of the prototype and update properties in the prototype, it updates for all elements. I understand that

Answer 1

Initialize mutable members in the constructor, not in the prototype. If it's in the prototype, it will be shared between all instances:

let Test = function () {
    this.array = [];
}

Test.prototype = {
    add: function (value) {
        this.array.push(value)
    }
}

let test1 = new Test();
let test2 = new Test();

test1.add(1);
test1.add(2);

console.log(test1.array);
console.log(test2.array);