radykl@gmail.com wrote:[color=blue]
> Can anyone explain me why you need to add open and close parenthesis to
> a JSON text in order to use eval() to parse it?
> For example:
>
> var json = "{a: 'abc', b: 'def'}";
> var obj1 = eval("(" + json + ")"); //ok!
> var obj2 = eval(json); //syntax error!
>
> why are parenthesis necessary?[/color]
For the same reson as:
{a: 'abc', b: 'def'};
causes an error but:
( {a: 'abc', b: 'def'} );
does not.
When encountered on the left hand side, the punctuator '{' defines the
start of a block statement, like if{... or while{... etc. The stuff
inside the block is evaluated as if it were a series of statements, so
the script engine attempts to evaluate:
a: 'abc', b: 'def'
and barfs (understandably).
By enclosing the expression in () it is evaluated as if it were the
right hand side of an expression, in which case {} is treated as an
object initialiser. So what you must pass to eval is:
( { /* property names & values */ } )
as a literal string to force it to treat the {} as an object
initialiser.
--
Rob
