Question

二十一点游戏：我在下面做了交易功能，它应该返回1-4之间的随机数，代表一个套装，以及另一个代表一个卡号的1-3之间的随机数。

当我通过调用console.log(getSuit(card1));测试代码时，它返回NaN

任何人都知道为什么？

// Make your card constructor again here, but make sure to use private
// variables!
function Card(num, suit){
    var num = num; 
    var suit = suit;
    getSuit = function(){
        return suit; 
    }; 
    getNumber = function(){
        return num; 
    };

    getValue = function(card){
        if (card > 10){
            return 10; 
        }else if (card === 1){
            return 11; 
        }else{
            return card; 
        }

    };

}

// Make a deal function here.  It should return a new card with a suit
// that is a random number from 1 to 4, and a number that is a random
// number between 1 and 13

var deal = function(){
    var suit = Math.floor(Math.random * 4 + 1);
    var number = Math.floor(Math.random * 13 + 1);
    return new Card(number, suit); 
}; 


// examples of the deal function in action
var card1 = deal();
var card2 = deal();

console.log(getSuit(card1));

Answer 1

只需在随机

之后添加（）即可

var deal = function() {
    var suit = Math.floor(Math.random() * 4 + 1);
    var number = Math.floor(Math.random() * 13 + 1);
    return new Card(number, suit);
};

Answer 2

你不应该打电话：

console.log(card1.getSuit());

Answer 3

你有一些复合问题，但你获得NaN的原因是你使用了随机函数。在调用方法/函数后，请包含()。

对Card类进行了其他更改。 this.将变量分配给该类实例。同样适用于这些功能。因此，这会改变您调用getSuit()的方式，作为方法调用。它之前有效，因为你的getSuit（）被放入了全局命名空间。

function Card(num, suit){
    this.num = num; 
    this.suit = suit;
    this.getSuit = function(){
        return suit; 
    }; 
    this.getNumber = function(){
        return num; 
    };

    this.getValue = function(card){
        if (card > 10){
            return 10; 
        }else if (card === 1){
            return 11; 
        }else{
            return card; 
        }

    };

}

var deal = function(){
    var suit = Math.floor(Math.random() * 4 + 1);
    var number = Math.floor(Math.random() * 13 + 1);
    return new Card(number, suit); 
}; 


// examples of the deal function in action
var card1 = deal();
var card2 = deal();

console.log(card1.getSuit());

Answer 4

变化：

var num = num; 
var suit = suit;

到

this.num = num; 
this.suit = suit;

等

Answer 5

试试这个：

// Make your card constructor again here, but make sure to use private 
// variables!
function Card(num, suit){
    // NOTE: "this."
    this.num = num;
    this.suit = suit;
    this.getSuit = function(){
        return this.suit;
    };
    this.getNumber = function(){
        return this.num;
    };

    this.getValue = function(card){
        if (card > 10){
            return 10;
        }else if (card === 1){
            return 11;
        }else{
            return card;
        }
    };
}

// Make a deal function here.  It should return a new card with a suit
// that is a random number from 1 to 4, and a number that is a random
// number between 1 and 13   
var deal = function(){
    // NOTE: Math.random()
    var suit = Math.floor(Math.random() * 4 + 1);
    var number = Math.floor(Math.random() * 13 + 1);
    return new Card(number, suit);
};

// examples of the deal function in action
var card1 = deal();
var card2 = deal();

// NOTE: card1.getSuit()
console.log(card1.getSuit());

Answer 6

您需要修复三件事：

您需要Math.random()上的parens。
您需要像getSuit()这样调用card1.getSuit()，而不是如何做到这一点。
您需要实际使getSuit，getNumber和getValue成为Card对象的方法。正如您已声明的那样，它们只是Card构造函数中的本地函数，并且无法从该构造函数外部调用。

制作这些函数方法有两种常用方法。一种是将它们分配给Card原型对象。另一种是将它们分配给构造函数中的this。

以下是将它们分配给原型对象的样子：

function Card(num, suit){
    this.num = num; 
    this.suit = suit;
}

Card.prototype = {
     getSuit: function() {
         return suit;
     },
     getNumber: function() {
         return num;
     },
     getValue: function(card) {
        if (card > 10){
            return 10; 
        }else if (card === 1){
            return 11; 
        }else{
            return card; 
        }
    }
};

// Make a deal function here.  It should return a new card with a suit
// that is a random number from 1 to 4, and a number that is a random
// number between 1 and 13

var deal = function(){
    var suit = Math.floor(Math.random() * 4 + 1);
    var number = Math.floor(Math.random() * 13 + 1);
    return new Card(number, suit); 
}; 


// examples of the deal function in action
var card1 = deal();
var card2 = deal();

console.log(card1.getSuit());

如果您希望num和suit保留私有变量，那么您必须像这样定义Card内部的方法：

// Make your card constructor again here, but make sure to use private
// variables!
function Card(num, suit){
    var num = num; 
    var suit = suit;
    this.getSuit = function(){
        return suit; 
    }; 
    this.getNumber = function(){
        return num; 
    };

    this.getValue = function(card){
        if (card > 10){
            return 10; 
        }else if (card === 1){
            return 11; 
        }else{
            return card; 
        }

    };

}

// Make a deal function here.  It should return a new card with a suit
// that is a random number from 1 to 4, and a number that is a random
// number between 1 and 13

var deal = function(){
    var suit = Math.floor(Math.random() * 4 + 1);
    var number = Math.floor(Math.random() * 13 + 1);
    return new Card(number, suit); 
}; 


// examples of the deal function in action
var card1 = deal();
var card2 = deal();

console.log(card1.getSuit());

Answer 7

此版本保留使用私有变量。请注意，函数参数是自动私有变量，因此您无需重新声明它们。

function Card(num, suit) {
    this.getSuit = function() {
        return suit;
    }; 
    this.getNumber = function() {
        return num;
    };
    this.getValue = function() {
        if (num > 10)
            return 10;
        if (num == 1)
            return 11;
        return num;
    };
}

为什么这段代码会返回NaN？

7 个答案: