Javascript syntax issue with returning an object literal

Question

var Tweet = Backbone.Model.extend({
  defaults: function()
  {
       return
       {
         author: ''
         status: ''
       }
  }
});

according to the syntax it should be

 author: '',
 status: ''

But this provides an error while the one in code working yet producing no output

score 3 · Accepted Answer · edited May 23 '17 at 11:50

3

You have fallen into a trap called automatic semicolon insertion. Specifically, there must not be a newline between return and {

var Tweet = Backbone.Model.extend({
    defaults: function() {
        return { // !!!
            author: '',
            status: ''
        }; // as a convention, I add ; always here, though not strictly needed.
    }
});

Otherwise Javascript considers this being 2 statements:

return;

which just returns the value undefined, and

{
   author: '';
   status: '';
}

which is a block compound statement, where there are 2 labels: author: and status:, each followed by a no-op string literal expression statement ''. Adding a , after the author: '' line makes it a syntax error, as a statement cannot end in a comma / the comma cannot be followed by a label.

edited May 23 '17 at 11:50

Community

1
1

answered May 08 '14 at 11:09

Antti Haapala -- Слава Україні

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Seriously..?? Yes that worked and moreover I have been coding on C/C++, Java etc and never saw this issue but amazed to read this. – MixedVeg May 08 '14 at 11:16
1

That's why you should use a linter, like JSLint, JSHint or ESLint. – anddoutoi May 08 '14 at 11:48
There are people who think that relying on ASI is a great thing, well I think it is a cancer :D – Antti Haapala -- Слава Україні May 08 '14 at 11:54
gr8 to know it, this is what happens when u come from a diverse coding background.! – MixedVeg May 11 '14 at 05:42

Javascript syntax issue with returning an object literal

1 Answers1