Javascript Prototyping Error

Question

最近我一直在研究Javascript原型，可以理解理論，並相信它對我的語言理解非常有用，但不能完全得到以下的工作...

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

每一個編譯器/檢查器在第2行標記'缺少分號'錯誤。 我很難過，但相信我忽視了一些非常簡單的事情。

有人能指出我正確的方向嗎？

Answer 1

你想說

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

？

Answer 2

引擎不知道super_player是function，直到您聲明爲一個，因此它沒有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

您對第1行的評論阻止了結束大括號。所以你有一個搖晃的開放式支架，它不起作用。你可以將它更改爲以下：

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

如果我是你，我覺得你要考慮使用駝峯類名執行以下操作：

function SuperPlayer() { 
} 

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

這將使SuperPlayer的基類，和Player作爲Player從SuperPlayer通過其原型繼承而派生的類。而不是像你在上面的例子中那樣。

Answer 4

你想要做這樣的事情

function Player() { 
    // player things here 

} 

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

假設SuperPlayer是超一流的球員，因爲它是。

編輯 - 如果SuperPlayer是一個更好的球員，也就是玩家的一個子類，只是扭轉上述格局

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 

我分不清你寫什麼，如果SuperPlayer是一個子類，或者沒有。此外，其他答案指出，您發佈的代碼在語法上由於評論而被破壞...

Answer 5

正在查看chubbards的答案...原型關鍵字可以被最好地描述爲笨拙..這很奇怪，因爲它確實是面向對象的，但實現是瘋狂的！

舉一個常見的例子...

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... 

這個怎麼樣，而不是？：

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? :} 

是正確的？ ：|

Answer 6

非常尊重你Chubbard。 :)

你的例子幫了很大忙。

我原來的'例子'是相當輕浮。 ：P

我還在跑成問題了一把，雖然... 要闡述我的「貓」樣品（保持事物儘可能簡短）：

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(); 

}); 

你是當然的權利，我鏈中的每個類都直接創建最終實例，是一個原型函數。但爲什麼（lion.name）工作，但沒有（lion.prototype.name）。相反，爲什麼lion.prototype.pounce（）可以工作，而lion.pounce（）是borks？

拿破崙和羅裏都是獅子畢竟...

我有負載更多的JavaScript的問題......這是一個非常奇怪的語言......;）