exercise 2: baby steps | new to node, not to JS and this baffles me

[Lowen Fan]

Hi guys, I've been programming quite a while in JS. But am a newbie to Node. What a great app learnyounode is!

But this baffled me, perhaps someone cal explain this to me:

'strict mode';

var result;

for (var i = 2; i < process.argv.length; i++) {

result += Number(process.argv[i]);

}

console.log(result);

This always returned NaN. When I console log each iteration, I always end up with an extra iteration which has the value of NaN. Adding them up results into NaN. 

But when I do this:

'strict mode';

var result = 0;

for (var i = 2; i < process.argv.length; i++) {

result += Number(process.argv[i]);

}

console.log(result);

Everything is fine and the program works as expected.

Who can enlighten me??

[Calogero Mandracchia]

Hi!

In JS you need to initialize a variable or it will be "undefined".

Even in the browser, you can try right now in the browser's console with "typeof result".

let result =+ Number() is:

result = undefined + Number() -> NaN

That's it!