Re: function pointers vs direct calling in javascript

getsanjay.sharma@xxxxxxxxx said the following on 11/22/2007 1:37 AM:
On Nov 21, 1:13 pm, Randy Webb <HikksNotAtH...@xxxxxxx> wrote:
Told ya you wouldn't believe me :)
I believe you. :-)

Is this so that it doesn't go out to search the
scope tree to look for 'tempVar2' or for some other reason?
That's a possibility, although it isn't in this case.
So you mean there are cases where this would be true? Any examples?

A case where I wouldn't want it to go outside looking for it?

var tempVar = new Array();
//lots of entries in tempVar here

function something(){
tempVar = "...."
}

function somethingElse(){
alert('hey, where did my array go?')
}

A case where I would? The altering of a global variable, an array, or several other things.

An detailed explanation with any relevant links would be greatly
appreciated.
Detailed explanation of the use of the var keyword? I am sure there is
one somewhere but I don't have a link to one. The simplest way to
remember it is that using var on a variable name in a function will
*never* alter a global variable. I always use it unless I explicitly
want to alter a global variable from within a function. The only other
time it can come into play is with inner functions and I never use them.
They give me too big a headache and I have never had a use for them.
Here is what I think of 'var', correct me if I am wrong.

'var' doesn't as such declare a variable. You don't need 'var' keyword
to *declare* variables or put them in the symbol tree in javascript.
It's just an indication to the scripting engine that 'please put this
variable in a scope which is local to this function. So saying:

var myArray = new Array();

Give it some thought :)

var a = 10;
var a = 11;

doesn't actually create two variables or declare two variables but
refer to the same variable both the times which is 'a' which was
declared and defined using the statement 'a = 10'. Thus prepending the
variable name with 'var' separates it from the global namespace
(scope) (assuming we are not using 'with' in which case we would have
an additional scope).

Is this good enough?

It isn't that simple though.

var someVar = "global variable";
function someFunction(){
var someVar = "local variable";
someVar = "modified in the function";
alert(window['someVar'])
}

Without testing, what will the alert say, and why? Then test it and see if you were right without testing it :)
--
Randy
Chance Favors The Prepared Mind
comp.lang.javascript FAQ - http://jibbering.com/faq/index.html
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/
.

Relevant Pages

  • Re: function pointers vs direct calling in javascript
    ... scope tree to look for 'tempVar2' or for some other reason? ... Here is what I think of 'var', correct me if I am wrong. ... 'var' doesn't as such declare a variable. ... a property of the global object when the code executes. ...
    (comp.lang.javascript)
  • Re: function pointers vs direct calling in javascript
    ... scope tree to look for 'tempVar2' or for some other reason? ... Detailed explanation of the use of the var keyword? ... to *declare* variables or put them in the symbol tree in javascript. ... variable in a scope which is local to this function. ...
    (comp.lang.javascript)
  • Re: function pointers vs direct calling in javascript
    ... //lots of entries in tempVar here ... starts searching for an identifier from the closest scope to the most generic scope. ... The use of the 'var' keyword stops it from going "up" the scope chain. ...
    (comp.lang.javascript)
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    ... >This one was proposed long ago as a way to declare a var whose scope is ... All sorts of things can work, ...
    (comp.lang.ruby)
  • Re: Using temporary table in in dynamic SQL
    ... is defined ouside the scope of dynamic sql statement. ... declare @var table ...
    (microsoft.public.sqlserver.programming)