javascript - Novice, let me ask a basic question about prototype expansion. Can you please give me some guidance?

Question

1. The third line of code is not understood.
The third line should be implemented. Add data as the prototype object to super_robot.
Why not SuperRobot.__proto__=data;
but say.__proto__=data; ??
2.

function SuperRobot(data) {
    var say = function() { return "Hello World!"; };
    say.__proto__=data;
    return say;
}

var data = { name:"atom", age: 5};
var super_robot = SuperRobot(data);

console.log(super_robot());            //Hello World!
console.log(super_robot.age);        //5
console.log(typeof super_robot);     //function

Answer 1

function Fun(){
    var a = {};
    return a;
}
var super = Fun();

Who should be added to at this timesuper等于什么？
是不是等于Fun内声明的a?
所以__proto_.

Answer 2

Writing like this is equivalent to rewriting the prototype chain of super_robot, which cannot be regarded as an extension. Originally, super_robot.__proto__ pointed to Function.prototype. After rewriting, super_robot.__proto__ pointed to the incoming data object. It can be said that after rewriting, super_robot can no longer be regarded as a It is a real function. Now it cannot use the methods on the Function prototype, such as call, apply, bind, etc.

console.log( super_robot instanceof Function ); // false
console.log( super_robot.call ); // undefined

If you extend it, you should write say.__proto__.name = name, say.__proto__.age = age, which is equivalent to Function.prototype.name = name, Function.prototype.age = age, but this will make all function instances accessible. Two attributes, so it is generally not recommended to expand like this

Answer 3

SuperRobot is just a factory function, what it returns is the core