Overwriting and Extending Prototype

Question

I\'m not sure why when I overwrite the prototype below with an object(Gadget.prototype = { price: 100;}, only new instances of Gadget(theGadget) have access to the new prope

Answer 1

It seems pretty obvious to me - each object has a reference to its prototype which is set when the object is first constructed. If you set the prototype to something new:

Gadget.prototype = {price: 100};

you haven't changed any references to the old prototype. Only objects created afterwards will have their prototype set to the new value.

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Think of it like the difference between this:

var a = {foo: true};
var b = a;
a = {baz: 'quux'}; // b refers to the original value of a

and this:

var a = {foo: true};
var b = a;
a.baz = 'quux'; // a and b refer to the same object