JavaScript Please help me explain this

[webdeveloper]

let isEven = (n) => {
 
    if (n === 0){
        return true
    } else if(n === 1){
        return false
    } else if(n < 0){
        return isEven(-n)
    }
    else {
       return isEven(n-2)
    }
  
}
console.log(isEven(-1))

How come that this result is false? shouldn't the result be true? I mean the expresion goes like this -1 - -1 = 0

 

[Malcolm]

@ChatGPT Can you help explain this thread?

 

[ChatGPT]

@ChatGPT Can you help explain this thread?

Of course! I'll be happy to help explain the code and clarify any confusion.

In the provided code, there is a function called isEven which takes a number n as an argument. This function is meant to determine whether the number is even or odd using recursion.

The function checks four cases:

1. If n is equal to 0, it returns true, indicating that it is an even number.
2. If n is equal to 1, it returns false, indicating that it is an odd number.
3. If n is a negative number, it recursively calls isEven with the positive value of n by using -n. This is done to handle negative inputs correctly.
4. For any other positive number, it recursively calls isEven by subtracting 2 from n until it reaches one of the base cases above.

Now, in the specific case where isEven(-1) is called, the function goes to the third case because -1 is a negative number. In this case, the function recursively calls isEven(-(-1)), which simplifies to isEven(1). Since 1 is an odd number, the function eventually returns false for isEven(-1).

So, the result of isEven(-1) is indeed false according to this code implementation. I hope that clears up any confusion, but feel free to ask if you have any further questions!

 

[JavaJames]

That is so scary

 

[Antero360]

let isEven = (n) => {
 
    if (n === 0){
        return true
    } else if(n === 1){
        return false
    } else if(n < 0){
        return isEven(-n)
    }
    else {
       return isEven(n-2)
    }
 
}
console.log(isEven(-1))

How come that this result is false? shouldn't the result be true? I mean the expresion goes like this -1 - -1 = 0

Hi there,
Question... what is the purpose of this code snippet? If it's to tell whether a number is even or odd... this unfortunately does not do that. There's a simpler way to do this

 

[JavaJames]

Obviously this is a teaching exercise in recursion, not a sensible way to do even/odd. But why do you think it doesn’t work?

 

[Antero360]

Obviously this is a teaching exercise in recursion, not a sensible way to do even/odd. But why do you think it doesn’t work?

To be honest with you, the code above does indeed work, I think what threw me off was that last if-statement