FAQ: Debugging JavaScript Code - Stack Overflow

This community-built FAQ covers the “Stack Overflow” exercise from the lesson “Debugging JavaScript Code”.

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Using the ternary operator returns ‘undefined’…

const containsCake = (string) => {
  string.includes('cake') ? true : false
}

Does anyone know why?

you don’t return anything? The keyword is missing

2 Likes

Thanks! So just to understand how ternary operators work, this statement…

const containsCake = (string) => {
  return (string.includes('cake') ? true : false)
}

is the equivalent to…

const containsCake = (string) => {
  if (string.includes('cake')) {
    return true
    } else {
    return false
  }
}

So it looks like if/else statements return the result automatically, but ternary operators don’t?

1 Like

The ternary operator is just a shorthand, it allows you to write a shorter condition.

no. I see return keywords in this code sample:

if (string.includes('cake')) {
    return true
    } else {
    return false
  }

if you do:

if (string.includes('cake')) {
    true
    } else {
    false
  }

you will also get undefined

the ternary operator does allow you to cut down the number of return keywords, you only have to use one return keyword vs 2 keyword with if/else.

JS does allow you to automatically return the result if the body of your function is only a single line:

const containsCake = (string) => string.includes('cake') ? true : false;

we could make this even smaller, if you only have a single parameter you can get rid of the brackets:

const containsCake = string => string.includes('cake') ? true : false;

furthermore, the includes method itself already returns a Boolean value, thus we can even do:

const containsCake = string => string.includes('cake');

but i suppose that beats the point of teaching the ternary operator.

why does your function have a parameter? You don’t even use it:

const containsCake = () => string.includes('cake');
1 Like

Super helpful!

I see I was mixing it up with the single line version. It’s cool that it can be shortened even further, and technically doesn’t need the ternary operator…

Good stuff, thanks!

Regarding your question, the (string) parameter was already included in the function declaration. According to the lesson instructions, the purpose of the containsCake function is to take a string and check if that string contains the substring 'cake' inside of it.

I tried omitting the (string) parameter, like in your last example, but it throws back an error.

string is needed, sorry, my mistake. you check if cake is included in string

you’re welcome :slight_smile:

i considered that possibility, which is why i showed the shorthand.

1 Like

The if statement is exactly how I did it, because the problem hinted towards using ‘if’. :slight_smile: