Calling a function within a loop, "Undefined is not a function"

Question

I have two functions at the top of my code. Below in a while (i<1) loop, I call one of the functions above. This works the first time, but the second time the function is called it displays an error:

TypeError: undefined is not a function

Below is the code:

var i = 0;
var newBalance = 0;
var deposit = function(amountIn)
{
    newBalance = (newBalance + amountIn).toFixed(2);
};
var withdrawl = function(amountOut)
{
    newBalance = (newBalance - amountOut).toFixed(2);
};
var choice = prompt("Would you like to access your account?").toLowerCase();
if (choice === "yes"){
    while (i<1){

        var inOrOut = prompt("Are you making a deposit or a withdrawl?").toLowerCase();
        var strAmount = prompt("How much money are you trasfering?");
        var amount = parseFloat(strAmount);

        if (inOrOut === "deposit")
        {
            deposit(amount);
        }
        else if (inOrOut === "withdrawl")
        {
            withdrawl(amount);
        }
        else
        {
            console.log("You did not enter a valid number");
        }

        console.log("Your new balance is $" + newBalance);
        var choiceTwo = prompt("Would you like to make another transaction?").toLowerCase();
        if (choiceTwo === "no")
        {
            i = i + 1;
        }
    }
}

I sincerely hope this is not a real financial transaction.... — BReal14
– BReal14, Commented Oct 3, 2014 at 13:58

ruakh · Accepted Answer · 2014-10-03 14:00:11Z

1

Initially, you set newBalance to a number. Calling either of your functions, however, will set newBalance to a string. (toFixed returns a string, not a number.) After that, newBalance + amountIn will also be a string (and be completely different from what you want — the + will denote string concatenation rather than addition), so it will not have a toFixed method. So you get the error you see.

To fix this, modify your functions so that they do not convert newBalance to a string. You should use toFixed only when you are displaying the balance:

console.log("Your new balance is $" + newBalance.toFixed(2));

answered Oct 3, 2014 at 14:00

ruakh

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