Javascript function for boolean returns

Question

I'm having some issues getting a proper boolean return on section 4.1 of Codecademy's Javascript tutorial. Here is the code:

// Define quarter here.
var quarter = function(n) {
    if (n / 4 ){
        return true;
    } else {
        return false;
    }
};

if (quarter(4) === 1) {
  console.log("The statement is true.");
} else {
  console.log("The statement is false.");
}

From what I can see, I am passing the newly defined quarter variable a function with a parameter of 'n' that I then divide by 4 to see if it returns 1 for true, or 0 (else) for false. I then am using the 'quarter' function in an if loop to check for equality of 1 of the number '4' passed as 'n'.

I'm assuming this is some basic logic that I am just not used to using (as a front end developer looking to get into JavaScript programming) but I would definitely appreciate some thoughts and guidance.

Pointy · Accepted Answer · 2012-04-23T18:57:00.283

16

In JavaScript, the constants true and false are not numbers; they're a separate type.

Furthermore, you're comparing with === and that will explicitly prevent type conversion during the comparison.

Note that n / 4 is going to be true (non-zero) for all values of "n" except 0 (edit you probably meant to use %). And in general, any construction of the form:

if (expression) {
  return true;
}
else {
  return false;
}

can be replaced by:

return !!(expression);

or, alternatively,

return Boolean(expression);

edited Apr 23 '12 at 18:57

answered Apr 23 '12 at 18:50

Pointy

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return !!(expression); is pretty horrible shortcut to boolean conversion but still - nice answer – Paul Sullivan Apr 23 '12 at 19:11
Well it's not really "horrible"; it's just idiomatic. But *chacun son goût* :-) – Pointy Apr 23 '12 at 20:30

score 3 · Answer 2 · answered Apr 23 '12 at 18:51

3

Change your if statement to be consistent, since 1 != true. The triple equals will not allow it.

if (quarter(4) == true) {

Your function is also incorrect, I think you want something more like this, to return if it's divisible by 4:

var quarter = function(n) {
  if (n % 4 == 0){
    return true;
  } else {
    return false;
  }
};

This can be shortened to this:

var quarter = function(n) {
   return n % 4 == 0;
}

answered Apr 23 '12 at 18:51

Developer

2,021
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2

Er... really? For the purposes of the question, this code is equivalent. – Dave Newton Apr 23 '12 at 18:52
Yes this code is equivalent - the % symbol will return 0 OR NOT 0. All positive integers will be interpreted as TRUE and 0 is false. So it is equivalent – Paul Sullivan Apr 23 '12 at 19:06
1

Oh, that's great. That shorthand definitely makes more sense. Thanks! – Matt Zelenak Apr 23 '12 at 19:41

score 3 · Answer 3 · edited May 23 '17 at 12:32

3

Using === means you're asking for a "strict equals"--not truthy or falsey. This means you can't check for a number, because a number is not strictly true. See this SO question for more details.

The calling code should either check for === true, or just skip the explicit value compare, and just be if (quarter(4)) { ....

edited May 23 '17 at 12:32

Community

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answered Apr 23 '12 at 18:51

Dave Newton

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Gabriel_Student_Innovated · Answer 4 · 2015-10-10T21:36:16.953

Couldn't find an answer on here that worked, so I assume I just missed it. I also find that Googling solutions make things worse for me.

I tend to find that I overthink the solutions in Javascript, and this obviously leads to an inability to solve the solutions.

You also don't necessarily need the return true, but I added it anyways.

Just remember that logically ordered simplicity is key.


    var quarter = function(number) {
        var number = n / 4;
        var n = 48;
    if (quarter(number) % 3 === 0 ) {
        console.log("The statement is true");
        return true;
    } else {
        console.log("The statement is false");
        }
    }

I hope that works for you.

I'll use my lack of JavaScript skill and knowledge to explain this to beginners like myself, and you. And anybody who has an extreme knowledge of JavaScript will probably disagree, but it's also why most programming employers will take a Communication major over a programmer anyday:

Define a function named quarter, meaning you are defining a function-- quarter -- but you must first define what quarter-- var.
```
var quarter = function(number) 
```
The function returns a value that equals to
```
n / 4
```
The function is being defined as
```
quarter(number)
```
The value is number.
You then introduce a new var that defines the value with
```
number = n / 4
```
To return true and begin your if statement,
```
function(number or n)
```
is now quarter, the function you're defining.
The basis of providing a correct equation relies on it returning true in the form of
```
console.log("The statement is true!")
```
You do this by then defining n with a number that will be divided 4, and then that number being able to be divided by 3 with no remainder.Since number
has been defined as
```
n / 4
```
, With n being defined as 48 in this example, both:
```
quarter(number)
```
and
```
quarter(n)
```
will work for the if / else statement.
To bring a remainder of 0 after dividing by 3, use
```
% 3 === 0
```
.
1. So
```
if (quarter(number) % === 3 {
```
  is now the defined function quarter.
```
number
```
  is a parameter, and you assign the value of the parameter with variables,
```
var number = n / 4
```
  and
```
var n = 48
```
  .

On that note, as I'm typing this, this would, in theory, also work and being shorter:


    var quarter = function(number) { 
              if (quarter(48) % 3 === 0) {
                 console.log("This statement is true!");
                 return number = number / 4;
              } else { 
                  console.log("This statement is false.");
            };
         };

score 0 · Answer 5 · answered Aug 25 '16 at 22:17

Okay, this stupid thing is super finicky. I'll demystify it right now. Your code should look like this:

var quarter = function (number) {
return number/4;
}
if (quarter(48) % 3 === 0 ) {
console.log("The statement is hella true");
} else {
console.log("The statement is hella false brah");
}

The reason you don't pass the module is because the stupid number in the quarter(n) bracket has to return with a true statement. Pick a number, any number and multiply that by (3) then by (4); which will in turn give you a value that makes the modulo % zero and making your if/else statement true.

My contribution to the world, -Aaron

Javascript function for boolean returns

5 Answers5