语法——原型prototype深入理解

console.log('-----------------------------Object');

var obj = {};
console.log(obj.__proto__ === Object.prototype);                // true
console.log(Object.prototype);                                  // Object
console.log(obj.prototype);                                     // undefined

console.log('-----------------------------Function');

// prototype is a Object property of a Function
var func = function () {};
console.log(func.__proto__ === Function.prototype);             // true
console.log(func.prototype === Function.prototype);             // false
console.log(func.prototype === Object.prototype);               // false

console.log(func.__proto__.__proto__ === Object.prototype);     // true
console.log(func.prototype.__proto__ === Object.prototype);     // true

console.log('-----------------------------new func');

// we look for say from this, then from __proto__ up
func.say = function () { console.log('func say'); }
func.__proto__.say = function () { console.log('func proto say'); }
func.prototype.say = function () { console.log('func prototype say'); }

// From this, we know that __proto__ is only used as pointer to find parent proto.
// And what the newed object has is determined by its prototype, and prototype.__proto__ etc.
//func.prototype.__proto__ = func.__proto__;

var new_func = new func();
new_func.say();
func.say();

// var new_func = {};
// new_func.__proto__ = func.prototype;
// func.call(new_func);

console.log(new_func.__proto__ === func.prototype);             // true
console.log(new_func.prototype);                                // undefined, as it's an Object

func.prototype.say = function () { console.log('func prototype say 2'); }
new_func.say(); // say 2

console.log('-----------------------------derived');

var de_func = function () {

};
de_func.prototype.__proto__ = func.prototype;

var new_de = new de_func();
new_de.say();

// remember:
// 1. var x = new obj(); means x.__proto__ = obj.prototype
// 2. we look for member from this first, then from this.__proto__