Hacker News Reader

Comment by TazeTSchnitzel | Hacker News Reader

It's due to parseInt having an optional second parameter, the radix, and map passing the index as the second paramater, hence:

  xs = [
    parseInt('10', 0),
    parseInt('10', 1),
    parseInt('10', 2)
  ]

View on HN

And since 0 is falsy we get 10 for base 0.

Which is odd. I wonder why they checked for falsiness and not the argument being undefined.

It's not exactly checking for falsy values. Although all falsy values will lead to a radix of 10 being applied.

parseInt internally uses the ToInt32 abstract operation on the radix parameter. Once it has that value, it explicitly looks to see if the value is 0. If it is, it uses a radix of 10.

https://people.mozilla.org/~jorendorff/es6-draft.html#sec-pa...

Edit: I hope that doesn't come off as pedantic. My point wasn't to disagree as much as it was to just add some further explanation.

This is HN, there's no such thing as being pedantic. :)

Or rather, there is but it's thoroughly welcome.

Although keep in mind that excessive pedantry is frowned upon.

Thank you. I read many comments to find an explanation.

It's not optional if you lint your code :)

Reply on news.ycombinator.com