Why do these identical (except whitespace) javaScript functions return different results

Question

I was trying this simple freecodecamp.org exercise, and was running into a problem with my solution.

What I can't work out is why these two functions return different results:

let someArray = {
  Person: {
    age: 27,
    online: true
  }
};


function works(obj) {
  return ('Person' in obj); 
}

console.log("works returns:" + works(someArray));

function doesNotWork(obj) {
  return  
    ('Person' in obj); 
}

console.log("doesNotWork returns:" + doesNotWork(someArray));

The results of running this on node.exe v10.8.0

Why is the second function returning undefined.

score 2 · Answer 1 · answered Aug 20 '18 at 09:30

2

You get undefined because there is a new line after return so it return undefined from doesNotWork function. Put that in a same line and it works:

let someArray = {
  Person: {
    age: 27,
    online: true
  }
};

function works(obj) {
  return ('Person' in obj);
}

console.log("works returns:" + works(someArray));

function doesNotWork(obj) {
  //should be in a same line
  return ('Person' in obj);
}

console.log("doesNotWork returns:" + doesNotWork(someArray));

answered Aug 20 '18 at 09:30

Ankit Agarwal

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Thanks but I know that (i.e. the other function). I'm asking why the behaviour is like that. – Preet Sangha Aug 20 '18 at 09:32
@PreetSangha because `return` keyword will return value which is a immediate successor. In your case it was a new line. – Ankit Agarwal Aug 20 '18 at 09:33
Thanks the dupe explained it all. – Preet Sangha Aug 20 '18 at 09:35

Why do these identical (except whitespace) javaScript functions return different results

1 Answers1