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Comment by meowface | Hacker News Reader

I actually think this looks really good, but 3 things:

1. Why differentiate it from CoffeeScript so much? Why not call it DOMCoffeeScript or something? Are there any core language changes from CoffeeScript other than the tag features?

2. I'm not sure how I feel about the mixture of XML tag characters with HAML/Jade-like indentation. My gut instinct is to always look for a closing tag with XML/HTML. Why not use some kind of sigil like % or @ or ! to represent a tag, since clearly the requirement for both a left and right caret is now obviated?

3. Why require the `var` keyword instead of making it the default? That's one of my biggest pet peeves with languages like Javascript and Lua. Local-by-default always makes the most sense.

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I can't speak to #1 and 2, but for #3, one of the criticisms of CoffeeScript has been that defining local variables and modifying variables from an outer scope have the same syntax. I.e., if I see `foo = 1` in a piece of code, I don't know if it's creating a local variable called foo or modifying a variable called foo from a containing scope -- the only way to tell is to scan all the containing scopes for a variable called foo. Even worse, let's say a piece of code had an inner function that declared a variable foo, but I then declare a variable called foo in an outer scope. That inner statement now silently switches from declaration to modification. I suspect this is why they force the use of `var` for declaration -- it disambiguates the two cases

1. Because the semantics are quite different. See my other post.

2. It's still nice to separate the attributes from the content:

    <h1 title="hello"> "Foo"

Why use a new syntax when everyone knows HTML/XML?

3. The lack of `var` in CoffeeScript is its worst feature ever IMO! Every time I write `someVariable = …` I'm terrified that I will accidentally overwrite a previous variable. Imba improves on JavaScript here and will correctly shadow multiple `var` in the same function.

People also know CSS query selectors...

    <label>
      <input:checkbox:checked#myCheckbox>
      <span> Some Text

Might be nicer than actually spelling out the attributes and properties, if you're taking an already wrist friendly language and bolting on tags, then taking that a step farther would probably be a nice idea as well.

Imba supports the syntax for IDs and classes:

    <label#foo.bar .baz=isBaz> "Label"

compiles to:

    ti$('label','foo').flag('bar').flag('baz',this.isBaz()).setText("Label").end()

where `flag` is a method which adds to the class list (unless the second argument is falsey).

Ok that is awesome.

After reading more, I agree with you on 1 and 2.

But for 3... so you never use languages like Ruby or Python? Variable assignment shadowing is always possible in those languages, yet for seasoned developers, it tends not to be a real issue.

#3. Python did the mistake of not having a var keyword. When you have nested closures you don't know if you are assigning a variable in the outer scope or the inner. You have to use hacks like creating an array of length 1 in the outer scope if you want to modify it in the inner scope otherwise you create new variables in the inner scope each time you try to make an assignment.

Now they created a new "nonlocal"-keyword to cope with this but it wasn't added until version 3.0. https://www.python.org/dev/peps/pep-3104/ has a great summary of all this.

Contrariwise, implicit creation of local variables is my biggest pet-peeve with languages like Python, so ymmv.

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