Coffeescript Syntax: Structure is wrong

Question

I simplified my code to show the problem. When I use this Coffeescript snippet:

$("<div>")
.text "hi"
.appendTo "body"

I expect it to compile like this:

$("<div>").text("hi").appendTo("body")

What it does instead is:

$("<div>").text("hi".appendTo("body"))

I found out that you can keep the brackets and it works, but I guess it's not the way you're supposed to write Coffeescript.

Can anyone tell me how I'm supposed to write it so it compiles to the desired output? Thank you very much.

I can see why the compiler would do that. You can't really expect the compiler to know what you want in that case. I suppose the language philosophy is to make a guess? — ChaosPandion
– ChaosPandion, Commented Aug 22, 2012 at 16:10
@ChaosPandion I think the compiler should do it that way it currently does if the last line would be indented... but I see your point, that's a problem with coffeescript — Jonny Burger
– Jonny Burger, Commented Aug 22, 2012 at 16:16
I don't see it as a problem really. The reason most languages require extra syntax to wrap method call arguments is to avoid such ambiguity. The fact that it is mostly optional in Coffeescript is nice but sometimes you have to help the compiler understand what you mean. — ChaosPandion
– ChaosPandion, Commented Aug 22, 2012 at 16:22
It may be tough to visualize but imagine you are parsing a potentially large amount of arguments. You reach the end of "hi" and everything is good so far. OK, now we have some white space here that's optional so I can mostly ignore it. OK so we have found a . after the first argument. Well I'm currently parsing arguments so this must be a method call on the "hi" so we begin treating the first argument as a method call. — ChaosPandion
– ChaosPandion, Commented Aug 22, 2012 at 16:30

Blake Taylor · Accepted Answer · 2012-08-22 16:36:40Z

4

Add the parentheses.

As far a good style goes, you should only omit syntax when it clutters your intent. In this case, omitting them loses your intent. Form follows function. You need the parentheses here inorder to declare precedent, and Coffeescript has support for them for that reason.

answered Aug 22, 2012 at 16:36

Blake Taylor

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Linus Thiel · Accepted Answer · 2012-08-22 19:06:56Z

3

I found out that you can keep the brackets and it works, but I guess it's not the way you're supposed to write Coffeescript.

Parentheses in CoffeeScript are optional, but that doesn't mean you're not supposed to use them. Feel free to use them! In some cases, like yours, they're even required.

To me, the big win with optional parentheses is for anonymous callbacks and other cases where the parentheses would otherwise span several lines, like this:

foo 'bar', (err, res) ->
  # Do stuff

Which, to me, is superior to

foo('bar', (err, res) ->
  # Do stuff
)

But even if that's your style, go for it!

So, to summarize, just write:

$("<div>")
  .text("hi")
  .appendTo("body")

Edit: Or even

$("<div>").text("hi").appendTo("body")

In this particular case, though, you could of course do:

$("<div>", text: "hi").appendTo("body")

TIMTOWDY ;)

edited Aug 22, 2012 at 19:06

answered Aug 22, 2012 at 16:37

Linus Thiel

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3 Comments

Jonny Burger Over a year ago

OK. Not so cool, but at least I know I wasn't missing some information. Thanks!

user508994 Over a year ago

$("<div>", text: "hi").appendTo("body") compiles to $("<div>", { text: "hi" }).appendTo("body"); ... not what you want.

Linus Thiel Over a year ago

@user508994: Why not? jQuery supports passing attributes as an object.

user508994 · Accepted Answer · 2012-08-23 04:17:58Z

0

coco and livescript (on npm or github) both are derived from coffeescript and are more "space sensitive", which allows you to do:

$ "<div>" .text "hi" .appendTo "body"

and

$("<div>")
  .text "hi"
  .appendTo "body"

which both compile to

$("<div>").text("hi").appendTo("body");

answered Aug 23, 2012 at 4:17

user508994

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