我的「賬戶餘額」變量沒有被代碼更新

Question

這段代碼基本上只是要求用戶該做什麼，然後使用2個函數來增加或減去我的實際變量的金額。但是，該變量未被代碼更新。我不明白爲什麼。

actbal = (100); 
confirm("Would you like to view account balance? Place a deposit? Or make a withdrawl? Press OK to continue!"); 

do 
{ 

var v = "VIEW"; 
var d = "DEP"; 
var w = "WITH"; 

var cont1 = prompt('Type: "VIEW" , "DEP" , or "WITH" to do their respective comands'); 

if(v === cont1.substring(0)) 
{ 
    confirm("Your account balance is: " + actbal); 

} 
else if (d === cont1.substring(0)) 
{ 
    var depo = prompt("How much do you want to deposit?"); 
    var cat = parseFloat(depo); 
    if(cat < 0) 
    { 
     alert("You cant Deposit a negative number..."); 
    } 
    else 
    { 

    confirm("Your new account balance is: " + deposit(cat)); 
    //var actbal = actbal + cat; 
    } 

} 
else if (w === cont1.substring(0)) 
{ 
    var With = prompt("How much do you want to withdrawl?"); 
    var dog = parseFloat(With); 
    if(dog < 0) 
    { 
     alert("You cant Deposit a negative number..."); 
    } 
    else 
    { 

    confirm("Your new account balance is: " + withdrawl(dog)); 
    } 

} 
else 
{ 
    alert("You have not entered a command correctly!"); 

} 
} 
while 
(
    confirm("Do you want to continue with your account?") 
); 


var deposit = function(cat) 
{ 
    actbal = +actbal +cat; 
    return +actbal +cat; 




}; 

var withdrawl = function (dog) 
{ 
    actbal = actbal - dog; 
    return actbal - dog; 

}; 

Answer 1

與您的代碼的問題是，你是在它們被定義的方式使用javascript函數在分析時而不是運行時。

實施例：

function deposit(amt) { 
    //do stuff here 
} 

是在運行時期間限定的，並且可以在代碼中的任何位置。

BUT

var deposit = function(amt) { 
    //do stuff here 
} 

期間分析時定義。

這意味着您應該將它放在代碼的頂部，否則變量函數「deposit」將在調用時未定義。

您的代碼的一個工作示例如下。

actbal = (100); 
confirm("Would you like to view account balance? Place a deposit? Or make a withdrawl? Press OK to continue!"); 

do { 

    var v = "VIEW"; 
    var d = "DEP"; 
    var w = "WITH"; 

    var cont1 = prompt('Type: "VIEW" , "DEP" , or "WITH" to do their respective comands'); 

    if (v === cont1.substring(0)) { 
     confirm("Your account balance is: " + actbal); 

    } else if (d === cont1.substring(0)) { 
     var depo = prompt("How much do you want to deposit?"); 
     var cat = parseFloat(depo); 
     if (cat < 0) { 
      alert("You cant Deposit a negative number..."); 
     } else { 

      confirm("Your new account balance is: " + deposit(cat)); 
      //var actbal = actbal + cat; 
     } 

    } else if (w === cont1.substring(0)) { 
     var With = prompt("How much do you want to withdrawl?"); 
     var dog = parseFloat(With); 
     if (dog < 0) { 
      alert("You cant Deposit a negative number..."); 
     } else { 

      confirm("Your new account balance is: " + withdrawl(dog)); 
     } 

    } else { 
     alert("You have not entered a command correctly!"); 

    } 
} 
while (
confirm("Do you want to continue with your account?")); 


function deposit (cat) { 
    actbal = +actbal + cat; 
    return actbal; // DO NOT DOUBLE ADD 




}; 

function withdrawl (dog) { 
    actbal = actbal - dog; 
    return actbal; // DO NOT DOUBLE SUBTRACT 

}; 

Answer 2

你必須在你調用它們之前定義你的函數。如果你只是重新排列它們，你會被罰款：http://jsfiddle.net/f4109zq9/

var withdrawl = function (dog){...} 
var deposit = function(cat){ ...} 

，然後你

do 
{ 
    ... 
} 
while(){ .... } 

Answer 3

有兩個問題。

首先，您在定義它們之前先調用deposit和withdrawl函數。如果您使用的語法：

function deposit() { 
    ... 
} 

你可以把定義的任何地方，但是當你使用賦值，它只有一次的腳本達到該行代碼生效。

其次，您在功能中添加和減去餘額兩次。您正在更新作業中的actbal函數，然後您在return聲明中再次添加/減去存款或提款金額。既然你已經更新actbal，你應該回到它，因爲它是：

var deposit = function (cat) { 
    actbal = +actbal + cat; 
    return actbal; 
}; 

var withdrawl = function (dog) { 
    actbal = actbal - dog; 
    return actbal; 
}; 

Answer 4

要麼使用function withdrawl()或他們你call之前寫的。其他人也一樣。並且不要在你的函數中使用add or subtract twice。