Question

我最近一直在研究Javascript原型，可以理解这个理论，并且相信它对我对语言的理解非常有用，但不能完全得到以下的工作......

var player = function(){//Declarations here};
var super_player.prototype = new player();

每个编译器/检查器在第2行标记“缺少分号”错误。我很难过，但相信我忽略了一些非常简单的东西。

有人能指出我正确的方向吗？

Answer 1

您想要做类似

的事情

function Player() {
    // player things here

}

Player.prototype = new SuperPlayer(); // get all the things on SuperPlayer prototype
Player.prototype.constructor = Player;

假设SuperPlayer是Player的超类，就像它一样。

编辑 - 如果SuperPlayer是一个更好的玩家，即玩家的子类，只需颠倒上述模式

function SuperPlayer() {
        // super player things here

    }

    SuperPlayer.prototype = new Player(); // get all the things on Player prototype
    SuperPlayer.prototype.constructor = SuperPlayer;  // the above line changed the     constructor; change it back

如果SuperPlayer是子类，我无法判断你写的是什么。此外，其他答案指出，由于评论...

，您发布的代码在语法上已被破坏

Answer 2

引擎不知道super_player是function，直到您将其声明为一个，因此它没有prototype。

var player = function () {},
    super_player = function () {}

// now we can happily set the prototype :)
super_player.prototype = new player();

// don't forget to point the constructor back to super_player
// not doing so will cause great confusion
super_player.prototype.constructor = super_player

Answer 3

您对第1行的评论阻止了结束括号。所以你有一个悬挂的开放式支架，不起作用。您可以将其更改为以下内容：

var player = function() {
   // Declarations here
};

如果我是你，我想你想考虑使用驼峰案例类名做以下事项：

function SuperPlayer() {
}

function Player() {
}
Player.prototype = new SuperPlayer();
Player.prototype.constructor = SuperPlayer;

这将使SuperPlayer成为基类，而Player作为Player的派生类通过它的原型从SuperPlayer继承。不像你上面的例子那样反过来。

Answer 4

你想说吗

super_player.prototype.player = function(){ /*Declarations here*/ };

Answer 5

再次查看chubbards的答案......原型关键字最好被描述为笨拙......这很奇怪，因为它肯定是OOP，但实现很疯狂！

举一个常见的例子......

mammal() = object;
cat() = prototype; // Implements mammal();
tiger() = object; // Implements cat(), but does NOT require the 'prototype' keyword... like some kind of 'cystalline' form? I can then create a whole range of individual 'tigers', but will not be able to add any new properties to any of them...

相反怎么样？：

machine() = object;
car() = prototype; // Implements machine. It's a machine afterall...
super_car = prototype; // It's a very fast car...
ferrari = prototype; // They only make supercars...
ferrari_355 = object; // One of the best cars they've ever made. No need to change it, right? :}

对吗？：|

Answer 6

非常尊重你的Chubbard。：）

你的榜样帮了很多忙。

我原来的“榜样”相当轻浮。：P

我仍然遇到一些问题但是...... 详细说明我的'猫'样本（保持尽可能简短）：

function mammal(){
// 'mammals' constructor - My 'empirical' 'class'...
} 
   mammal.count = 0; // To keep track of the zoo I've created. No subclass can access this property. It's a 'static' property

   // I could have declared this 'method' inside of my constructor
   // with an anonymous function attached to (this.prototype.breathe).

    mammal.track = function (){
        this.count++;
    }

    mammal.prototype.breathe = function(){
        alert("Inhale... Exhale...");
    }

function cat(){
// 'cat' constructor
}

// All cats shall now become a type of mammal
cat.prototype = new mammal();

cat.prototype = function(){
// This anonymous function is the REAL constructor for my 'cat' 'superclass'
}

    cat.prototype.meow = function(){
        alert("Meow!");
    }

function lion(){
// The king of jungle...
// I can keep track of the number of 'mammal' instances I create here
mammal.track();
}

// All lions are cats, afterall...
lion.prototype = new cat();
// Also note that I have no plans to extend the lion class.
// I have no need of a class below the 'idea' of a lion 

    lion.name = "Kitty"; // :}

    // Here's where I get confused...
    // I can set (lion.name) via instances, can't call (lion.pounce), but (lion.prototype.roar) works all day long! o_0
    lion.pounce = function(){
        alert(this.name+" pounces...")
    }

    lion.prototype.roar = function(){
        alert(this.name+" doesn't meow, he ROOOAAARS!"); 
    }

// With these constructs in place, I can now script...
$(document).ready(function(){

      var rory = new lion();    
      var napoleon = new lion();

      alert("We have "+mammal.count+" mammals running about");

          // This is 'Rory'...
          rory.name = 'Rory'; // Respect the pun...
          rory.roar();

          // This is 'Napoleon'...
          napoleon.name = 'Napoleon';
          napoleon.breathe(); // Napoleon can't breathe... he didn't inherit mammal.prototype.breathe(), for some reason
          napoleon.roar(); // How am I able to set (lion.name), but not call lion.pounce()?
          napoleon.pounce();

});

你当然是正确的，我的链中的每个类直到创建最终实例，都是原型函数。但为什么（lion.name）工作但不工作（lion.prototype.name）。相反，当lion.pounce（）borks时，为什么lion.prototype.pounce（）可以工作？

拿破仑和罗里都是狮子会毕竟...

我加载了更多Javascript问题......这是一种非常奇怪的语言......;）

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Javascript原型设计错误