Javascript prototype , __proto__

Question

When I execute below java script code I get error at "v.dummy();" line , please let me know where am I doing wrong.

 function Test()
 {
 }
 Test.prototype.foo = function () {
 console.log('foo');
 }
 var v = new Test();
 v.foo();
 v.__proto__ = function dummy() {
 console.log('__proto__'); 
 };
 v.dummy(); // Uncaught TypeError: v.dummy is not a function

Answer 1

__proto__ is just a reference of an object

IMG

You can't make it equal a new function, but you can do it like this:

v.__proto__.foo = function dummy(){}

Answer 2

I don't know what you are trying to do, but:

1) when you assign function to a variable, you may omit the name (dummy) and use an anonymous function (without a name). Function name is useless in this case. And if you do

var x = function y(){ ... }

you can call it like this: x(), not (削除) y() (削除ここまで)

2) __proto__ should be an object, not a function

usage of foo is correct, therefore it works.

You may want to consider reading a good JS book.

• refactor: I made below change and it worked v.__proto__ = { dummy: function () { console.log('proto'); } }; My assumption was function is also an object in java script. May be as you said i need to read JS good parts.
• Dmitry Gonchar: @CleanCrispCode Yes, function is an object in js. In your code you can call your function with v.__proto__(). But you should NOT do this, because __proto__ is an inner object used by javascript (to search the prototype chain to resolve methods it cannot find in the object itself). There are a lot more that can be told about prototypes, therefore I recommended a book