JavaScript function is returning NaN

Question

I have a function and it is supposed to return a number but instead it is returning NaN. Here is the code

function priceCalc(cust, transit, passType){

    var price = 0;
    if (passType === "monthly"){
      if (cust === "student" || cust === "elderly"){
        price = transit.monthly / 2;
      } else if (cust === "transit worker"){
        price = 0;
      } else {
        price = transit.monthly;
      }

    } else if (passType === "pre paid"){
      if (cust === "transit worker") {
        price = Infinity;
      } else {
        value = prompt('How much would you like on your pass?');
        price = parseInt(value);
      }

    }
    return price;

  };

price is the variable that is supposed to have a number value when it is returned, for instance when I pass in student for the cust param, bus for the transit param(which has a monthly attribute which is 60), and monthly for the pass type param it should return 30, but instead I get NaN. I'm running a Jasmine test on it which is this

describe('the application', function(){
  describe('publicPrice function', function(){

    it('takes in customer status, transit choice, and pass choice to calculate a price', function(){
      expect(App.priceCalc('adult', 'commuter rail', 'monthly')).toBe(80);
      expect(App.priceCalc('student', 'commuter rail', 'monthly')).toBe(40);
      expect(App.priceCalc('elderly', 'subway', 'monthly')).toBe(35);
      expect(App.priceCalc('transit worker', 'bus', 'monthly')).toBe(0);
    });
  });

});

And the function is part of this module if that matters

var App = (function(){
  var Transport = function(mode, monthly, prepaid){
    this.mode = mode;
    this.monthly = monthly;
    this.prepaid = prepaid;
  };

  var commuterRail = new Transport('commuter rail', 80, 5);
  var bus = new Transport('bus', 60, 2);
  var subway = new Transport('subway', 70, 3);

  var customerStatus = prompt('Please enter your status. \nAdult \nElderly \nStudent \nTransit worker');
  var transitInput = prompt('Please select your method of transport: \ncommuter rail \nbus \nsubway');
  var passSelection = prompt('Please select a pass: \nMonthly \nPrepaid');

  var transitMethod;

  if(transitInput === "commuter rail"){
    transitMethod = commuterRail;
  } else if(transitInput === "bus"){
    transitMethod = bus;
  } else if (transitInput === "subway"){
    transitMethod = subway;
  }

  console.log(transitMethod);

  function priceCalc(cust, transit, passType){

    var price = 0;
    if (passType === "monthly"){
      if (cust === "student" || cust === "elderly"){
        price = transit.monthly / 2;
      } else if (cust === "transit worker"){
        price = 0;
      } else {
        price = transit.monthly;
      }

    } else if (passType === "pre paid"){
      if (cust === "transit worker") {
        price = Infinity;
      } else {
        value = prompt('How much would you like on your pass?');
        price = parseInt(value);
      }

    }
    return price;

  };

  var publicPrice = function(customerStatus, transitMethod, passSelection){
    return priceCalc(customerStatus, transitMethod, passSelection);
  };

  priceCalc(customerStatus, transitMethod, passSelection);

  return {
    // publicPrice: publicPrice,
    priceCalc: priceCalc
  };

})();

App.priceCalc('student', 'commuter rail', 'monthly') You're passing the string commuter rail for transit, instead of an object. — Barmar
– Barmar, Commented May 11, 2015 at 20:57

lucky7id · Accepted Answer · 2015-05-11 21:01:05Z

3

price = transit.monthly / 2;

Here you are telling the interpreter to use property monthly of object transit. In your code transit is a string so transit.monthly evaluates to undefined

undefined / 2 evaluates to NaN

I think you mean to pass in the variable objects you created instead of the string.

answered May 11, 2015 at 21:01

lucky7id

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1 Comment

rdeg Over a year ago

Haha I can't believe I didn't notice that Thanks!

floribon · Accepted Answer · 2015-05-11 20:56:41Z

0

transit.monthly is likely a String, you should parse it before you do calculus on it:

function priceCalc(cust, transit, passType){

var price = 0;
if (passType === "monthly"){
  if (typeof transit.monthly === 'string') {
    transit.monthly = Number(transit.monthly);
  }
  if (cust === "student" || cust === "elderly"){
    price = transit.monthly / 2;
  } else if (cust === "transit worker"){
    price = 0;
  } else {
    price = transit.monthly;
  }

} else if (passType === "pre paid"){
  if (cust === "transit worker") {
    price = Infinity;
  } else {
    value = prompt('How much would you like on your pass?');
    price = parseInt(value);
  }

}
return price;

};

answered May 11, 2015 at 20:56

floribon

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4 Comments

Kevin Boucher Over a year ago

Interestingly ... "60"/2 returns 30. I'd like to see the value of transit.monthly at runtime.

JFM Over a year ago

Number("60")/2 should play safer though

Barmar Over a year ago

Javascript will automatically convert a string to a number when you pass it to an arithmetic operator, so this isn't the problem.

floribon Over a year ago

Indeed my bad, the problem comes from undefined as answered by lucky2id. Worth noting, null / 2 seems to be 0

Nicholas Thomson · Accepted Answer · 2015-05-11 21:01:00Z

0

Your function expects three parameters:

function priceCalc(cust, transit, passType){}

In your tests, your passing a string as the second parameter transit, but the function is written as if transit is an object. So in your priceCalc function when you do:

price = transit.monthly / 2

price is set to NaN

It looks to me like the priceCalc function expects a Transport object.

answered May 11, 2015 at 21:01

Nicholas Thomson

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Comments

Amit · Accepted Answer · 2015-05-11 21:01:57Z

0

You're passing a string into transit, where you probably meant to pass an object of class Transport.

If you add this code (yours):

if(transit === "commuter rail"){
    transit = commuterRail;
  } else if(transit === "bus"){
    transit = bus;
  } else if (transit === "subway"){
    transit = subway;
  }

to the beginning of your function, it will probably work.

answered May 11, 2015 at 21:01

Amit

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Comments

Barmar · Accepted Answer · 2015-05-11 21:02:16Z

You need to put the code that converts the names of transit methods to their corresponding objects into the priceCalc function:

  function priceCalc(cust, transit, passType){

    var price = 0;
    if(transit === "commuter rail"){
        transit = commuterRail;
    } else if(transit === "bus"){
        transit = bus;
    } else if (transit === "subway"){
        transit = subway;
    }

    if (passType === "monthly"){
      if (cust === "student" || cust === "elderly"){
        price = transit.monthly / 2;
      } else if (cust === "transit worker"){
        price = 0;
      } else {
        price = transit.monthly;
      }

    } else if (passType === "pre paid"){
      if (cust === "transit worker") {
        price = Infinity;
      } else {
        value = prompt('How much would you like on your pass?');
        price = parseInt(value);
      }

    }
    return price;

  };

The code that you currently have that does this with the transitInput variable is useless, since that variable doesn't have a value.

dotnetCarpenter · Accepted Answer · 2015-05-11 21:02:47Z

0

You get NaN because you try to divide "commuter rail" with 2.

App.priceCalc('student', 'commuter rail', 'monthly') -> price = transit.monthly / 2; where transit is "commuter rail". You should probably use an object with a monthly property.

answered May 11, 2015 at 21:02

dotnetCarpenter

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1 Comment

Barmar Over a year ago

No, he's trying to divide "commuter rail".monthly by 2.

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