How to avoid CoffeeScript method variables getting wrapped in object literals?

Question

CoffeeScript wraps variables declared inside methods in an object literal.

So, this:

@Templates =
    get: (templateName) ->
        result: ''              # DECLARED HERE
        $.ajax(
            'Views/Templates/' + templateName + '.html',
            type: 'GET'
            dataType: 'html'
            success: (data) ->
                result = data   # ASSIGNED HERE
            async: false
        )
        return result           # RETURNED HERE

Becomes this:

(function() {

  this.Templates = {
    get: function(templateName) {
      ({
        result: ''                  //DECLARED IN AN OBJECT LITERAL - I DON'T WANT THIS
      });
      $.ajax('Views/Templates/' + templateName + '.html', {
        type: 'GET',
        dataType: 'html',
        success: function(data) {
          var result;               //DECLARED LOCAL TO THE CALLBACK - I DON'T WANT THIS
          return result = data;
        },
        async: false
      });
      return result;                //RETURNED HERE - UNASSIGNED
    }
  };

}).call(this);

But what I need, and that works for me, is this:

(function() {

  this.Templates = {
    get: function(templateName) {
      var result = ''               //DECLARED HERE
      $.ajax('Views/Templates/' + templateName + '.html', {
        type: 'GET',
        dataType: 'html',
        success: function(data) {
          return result = data;     //ASSIGNED HERE
        },
        async: false
      });
      return result;                //RETURNED HERE
    }
  };

}).call(this);

What am I doing wrong? How can I fix this?

That's not a closure it's an object literal and it's wrapped with parentheses so that it wouldn't be treated as a block — Esailija
– Esailija, Commented Feb 21, 2012 at 15:26
I forgot to mention I am new to CoffeeScript and also Javascript. Thanks all for the answers and tips. — Rafael Romão
– Rafael Romão, Commented Feb 22, 2012 at 18:06

T.J. Crowder · Accepted Answer · 2012-02-21 15:27:40Z

4

What you've called a closure isn't a closure (closures in JavaScript are always functions). It's an object literal wrapped in parentheses.

I'm not really au fait with CoffeeScript, but if you want result to be a local variable in the get function, I believe you want to change

result: ''

to

result = ''

The former is the object initializer format (hence it getting translated into an object literal), the latter is a variable assignment. Seems to be covered on the CoffeeScript site under lexical scoping.

answered Feb 21, 2012 at 15:27

T.J. Crowder

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Comments

Nikita Volkov · Accepted Answer · 2012-02-21 15:33:55Z

2

By result: '' you declare a property of an object. What you needed was to declare a local variable by result = '':

get: (templateName) ->
    result = ''              # DECLARED HERE
    $.ajax(
        'Views/Templates/' + templateName + '.html',
        type: 'GET'
        dataType: 'html'
        success: (data) ->
            result = data   # ASSIGNED HERE
        async: false
    )
    return result           # RETURNED HERE

answered Feb 21, 2012 at 15:33

Nikita Volkov

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Comments

loganfsmyth · Accepted Answer · 2012-02-22 18:38:12Z

2

Why are you using a :? It's not being wrapped in a closure, you are just defining an anonymous object expression.

Just do this:

result = ''

That said, why are you doing a synchronous GET? That's very frowned upon and will make your site must less responsive.

edited Feb 22, 2012 at 18:38

answered Feb 21, 2012 at 15:30

loganfsmyth

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