How do I comment in CoffeeScript? "/* this */" doesn't work

coffeescript code-formatting comments block-comments

75,582

Solution 1

Use a single # sign

# like this

One character seems pretty minimal ;)

Also:

###
This block comment (useful for ©-Copyright info) also gets 
passed on to the browsers HTML /* like this! */
###

Solution 2

The main way to comment is sh/Perl/Ruby/... style # comments:

# This comment goes to the end of the line
# and it won't appear in the "compiled"
# JavaScript version.

You use the block style ### comments when you want a comment to appear in the JavaScript version:

Sometimes you'd like to pass a block comment through to the generated JavaScript. For example, when you need to embed a licensing header at the top of a file. Block comments, which mirror the syntax for heredocs, are preserved in the generated code.

So if you start with

###
PancakeParser is Public Domain
###

then you'd get this JavaScript comment in the generated JavaScript:

/*
PancakeParser is Public Domain
*/

Solution 3

Beware of ###! If you use ### to separate sections of code (as I do) it's awfully surprising when that code stops working as a result.

75,582

Eric Hu

Github: https://github.com/eric-hu

Updated on October 20, 2022

Comments

Eric Hu over 1 year
In what ways can you comment in CoffeeScript?

The documentation say you can use three hash symbols to start and close a comment block:
```
###
  Comments
  go
  here
###
```
I've found that I can sometimes use the following two formats
```
`// backticks allow for straight-JavaScript,
 // but the closing backtick can't be on a comment line (I think?)
`
```
Are there a simpler way to insert short comments in CoffeeScript?

Do NOT use this style**

Since this is getting a lot of views, I want to emphasize that
```
/* Comment goes here */
```
produces a MATH error when the /* is on its own line.

As Trevor pointed out in a comment on the question, this is a regular expression, NOT a comment!
- Trevor Burnham over 12 years
  
  If a /*...*/ comment "works," it's because the CoffeeScript compiler is interpreting it as a regex. Definitely not recommended!
- Pete Alvin about 10 years
  
  So I guess there is NO WAY in CoffeeScript to have an intra-statement (between characters) comment?
Aaron Dufour over 12 years

This is usually how you will want to comment; the triple hash is most often used when you want the comment to fall through to the javascript (copyright messages, usually).
Gerry almost 12 years

Ah sigh. The official docs use the single # form all through their examples, but never actually mention it in the text explanations, it only talks about the block comments.
Azat over 10 years

Do you know why? We have the code working locally but not on the build server with ###.
Mark Wilden over 10 years

Unfortunately, I noticed this months ago, and I'm not "in that space" right now to have a look at it.
Admin over 10 years

Because a pair makes a block comment?
nilskp over 9 years

Unfortunately no way to have block comments that don't show up in output.
Nick Perkins almost 9 years

Would not be so surprising if you used a syntax-highlighting editor, with comments appearing in a different color
Jim Mack over 7 years

Why downvote? It's a valid warning. Really, it's saying don't use a solid line of # as a section separator, or you may occasionally get unbalanced block comment pairs.