You guys should stop trolling each other and try to be helpful. This is an
area of js fraught with both FUD and wtfjs. Better to educate than to spout
personal anecdotes and one off edge cases. Mark has the right idea by
saying pick the technique that "does what you want". But you have to know
the difference in order to do that. And you can't assume that what you want
is what everyone always wants. This is an implementation detail.
And finally don't ignore the most obvious and important difference.
parseInt... parses integers! It will always try to give you back an
integer. Whatever your value is, you will get an integer or you will get
NaN. It will try to do this with improperly formatted strings as long as
they start with a parse-able number, e.g. "100px". This is either a nice
feature, or something to be avoided, depending on how well you've validated
your input. On the other hand, number conversion is part of the standard
language grammar. It uses well defined (but not necessarily intuitive)
rules to take a value and give you a number that may or may not have a
decimal component, or if it can't, it'll give you NaN. But it also respects
alternate number formats that are valid like exponential notation, e.g.
Number("10e2") === 1000. Using the unary "+" operator in front of a value
is strictly equivalent to calling Number().
Now, all of that being said, I think it's clear that both of these violate
principle of least surprise once you get into edge cases. They will both
screw you at some point or another if you don't control your input and
validate your output. So which one you should use isn't an "always" thing
and it has nothing do with what you find "more readable". Understand them
both, and pick the one that works for what you're doing.
:Marco
On Wednesday, February 22, 2012 10:18:57 AM UTC-8, Mark Hahn wrote:
>
> > +'123 px'
> > NaN
>
> And that is exactly correct. '123 px' is not a number. Using that
> "feature" is worse than trusting type coercion. I would never trust that
> in my code, just as I always use === instead of ==. Well actually I use
> "is" in coffee, but that is a different subject.
>
> What if your string was accidentally "100%" instead of "100 px"?
>
> You said nothing is right for me. I'm just pointing out that was an
> overly broad statement. Using + instead of parseInt *is* exactly right for
> me.
>
> If you want to be able to use '010' to represent 8 and '1xyz' to represent
> 1, then more power to you. I myself will never use parseInt. Not only for
> the behavior but because it takes too much typing, is less succinct and
> therefore is less readable.
>
> Compare...
> area = +w * +h
> To ...
> area = parseInt(w, 10) * parseInt(h, 10)
>
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