On 21/02/2013 19:40, piterrr.dolin...@gmail.com wrote:
<snip>
I am nervous about using variables "out of the blue", without having
to declare them. For example, when I write "i = 0" it is perfectly OK
to Python without 'i' being declared earlier. How do I know that I
haven't used this variable earlier and I am unintentionally
overwriting the value? I find I constantly have to use the search
facility in the editor, which is not fun.
You see, Javascript, for one, behaves the same way as Python (no
variable declaration) but JS has curly braces and you know the
variable you have just used is limited in scope to the code within
the { }. With Python, you have to search the whole file.
No, JavaScript - or better, ECMAScript -, does have variable
declaration. If you don't declare a variable with the "var" statement it
will become an unintentional global variable which is a very bad thing.
If the variable statement occurs inside a Function Declaration, the
variables are defined with function-local scope in that function.
Otherwise, they are defined with global scope (that is, they
are created as members of the global object. Variables are created when
the execution scope is entered. A Block { } does not define a new
execution scope.
PS.: JavaScript is a trademark, and the actual language name is
specified as ECMAScript.
See <http://ecma-international.org/ecma-262/5.1/>
--
Joao Rodrigues (J.R.)
--
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