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When you need to change the prototype of an object that already exists, how much faster is it to use proto where supported instead of copying the object.

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>
<script>
  Benchmark.prototype.setup = function() {
    var A = function(a1, a2) {
        this.a1 = a1;
        this.a2 = a2;
        };
    var B = function(b1, b2) {
        this.b1 = b1;
        this.b2 = b2;
        };
    var AA = function(a1, a2, a3) {
        A.call(this, a1, a2);
        this.a3 = a3;
        };
    
    // (new AA(1, 2, 3)) instanceof A === true
    AA.prototype = Object.create(A.prototype);
    
    var originalAA = new AA(1, 2, new B(new A(4, 5), new A(6, 7)));
    var serialized = JSON.stringify(originalAA);
    var deserialized = JSON.parse(serialized);
  };
</script>

Test runner

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deserialized.__proto__ = AA.prototype;
deserialized.a3.__proto__ = B.prototype;
deserialized.a3.b1.__proto__ = A.prototype;
deserialized.a3.b2.__proto__ = A.prototype;

deserialized.a3.b1 = $.extend(Object.create(A.prototype), deserialized.a3.b1);
deserialized.a3.b2 = $.extend(Object.create(A.prototype), deserialized.a3.b2);
deserialized.a3 = $.extend(Object.create(B.prototype), deserialized.a3);
deserialized = $.extend(Object.create(AA.prototype), deserialized);

deserialized = new AA(deserialized.a1, deserialized.a2, new B(new A(deserialized.a3.b1.a1, deserialized.a3.b1.a2), new A(deserialized.a3.b2.a1, deserialized.a3.b2.a2)));

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