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Simple parameter passing within a setInternal() call?

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  Simple parameter passing within a setInternal() call? Tuxedo <tuxedo@mailinator.com> - 2012-02-11 20:04 +0100
    Re: Simple parameter passing within a setInterval() call? Tuxedo <tuxedo@mailinator.com> - 2012-02-11 20:39 +0100
      Re: Simple parameter passing within a setInterval() call? Dr J R Stockton <reply1206@merlyn.demon.co.uk> - 2012-02-12 22:02 +0000
    Re: Simple parameter passing within a setInternal() call? Andreas Bergmaier <andber93@web.de> - 2012-02-11 21:39 +0100
      Re: Simple parameter passing within a setInternal() call? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-11 22:06 +0100
        Re: Simple parameter passing within a setInternal() call? Andreas Bergmaier <andber93@web.de> - 2012-02-11 22:33 +0100
          Re: Simple parameter passing within a setInternal() call? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-11 23:44 +0100
            Re: Simple parameter passing within a setInternal() call? Andreas Bergmaier <andber93@web.de> - 2012-02-12 03:04 +0100
          Re: Simple parameter passing within a setInterval() call? Tuxedo <tuxedo@mailinator.com> - 2012-02-12 09:22 +0100

#11705 — Simple parameter passing within a setInternal() call?

How can a simple string parameter be passed between two functions while 
inside a setInterval call? For example:

function initialFunction(x){
alert(x);
setInterval('repeatingStuff(x)',5000);
}

function repeatingStuff(x){
alert(x);
}
...

<a href="..." onclick="initialFunction('param_x');">stuff</a>

But the error "x is not defined" results from ..Stuff(x) in 
setInterval('repeatingStuff(x)',5000). How can the parameter between the 
two functions be passed within the setInteval bit?

Many thanks,
Tuxedo

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#11706 — Re: Simple parameter passing within a setInterval() call?

Tuxedo wrote:

[...]

> setInterval('repeatingStuff(x)',5000). How can the parameter between the

I thought I had tried this already but I must have simply got the quoting 
wrong. Of course, this works:
setInterval('repeatingStuff("' + x + '")',5000);

Tuxedo

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#11733 — Re: Simple parameter passing within a setInterval() call?

In comp.lang.javascript message <jh6g5k$bfn$1@news.albasani.net>, Sat,
11 Feb 2012 20:39:32, Tuxedo <tuxedo@mailinator.com> posted:

>Tuxedo wrote:
>
>[...]
>
>> setInterval('repeatingStuff(x)',5000). How can the parameter between the
>
>I thought I had tried this already but I must have simply got the quoting
>wrong. Of course, this works:
>setInterval('repeatingStuff("' + x + '")',5000);

That will use the value of x at call time, if x is simple or an
expression.

Another way is to pass x as a global variable; or, perhaps more clearly,
as a property of a global Object reserved and named, or otherwise
suitable, for the purpose.  Actually, repeatingStuff is such an Object.

That eliminates conversions to/from String, which may be inexact.

-- 
 (c) John Stockton, Surrey, UK.  ?@merlyn.demon.co.uk   Turnpike v6.05   MIME.
   Web  <http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
 Proper <= 4-line sig. separator as above, a line exactly "-- " (SonOfRFC1036)
 Do not Mail News to me. Before a reply, quote with ">" or "> " (SonOfRFC1036)

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#11707

Tuxedo schrieb:
> How can a simple string parameter be passed between two functions while
> inside a setInterval call? For example:
>
> function initialFunction(x){
> alert(x);
> setInterval('repeatingStuff(x)',5000);
> }
>
> function repeatingStuff(x){
> alert(x);
> }
> ...
>
> <a href="..." onclick="initialFunction('param_x');">stuff</a>
>
> But the error "x is not defined" results from ..Stuff(x) in
> setInterval('repeatingStuff(x)',5000). How can the parameter between the
> two functions be passed within the setInteval bit?

x must be in the scope of the second function. Therefore, you should 
define repeatingStuff inside the initialFunction:

function initialFunction(x){
    alert(x);
    function repeatingStuff(x){
       alert(x);
    }
    setInterval(repeatingStuff,5000);
}

or shorter:

function initialFunction(x){
    alert(x);
    setInterval( function(x){
       alert(x);
    }, 5000);
}

You should pass a function to setIntervall/Timeout, instead of a code to 
be evaluated each time (slow & buggy).

Another alternative is to use bind() or other functions, to return a 
function which calls repeatingStuff with the needed parameters:

function repeatingStuff(){...}
function initialFunction(x){
    alert(x);
    setInterval( repeatingStuff.bind(this, x), 5000);
}

Greetings,
  Bergi

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#11708

Andreas Bergmaier wrote:

> Tuxedo schrieb:
>> How can a simple string parameter be passed between two functions while
>> inside a setInterval call? For example:
>>
>> function initialFunction(x){
>> alert(x);
>> setInterval('repeatingStuff(x)',5000);
>> }
>>
>> function repeatingStuff(x){
>> alert(x);
>> }
>> ...
>>
>> <a href="..." onclick="initialFunction('param_x');">stuff</a>
>>
>> But the error "x is not defined" results from ..Stuff(x) in
>> setInterval('repeatingStuff(x)',5000). How can the parameter between the
>> two functions be passed within the setInteval bit?
> 
> x must be in the scope of the second function.

In the scope _chain_.

> Therefore, you should define repeatingStuff inside the initialFunction:
> 
> function initialFunction(x){
>     alert(x);            ^
            ^--------------'
>     function repeatingStuff(x){
                              ^
>        alert(x);            |
               ^--------------'
>     }
>     setInterval(repeatingStuff,5000);
> }
> 
> or shorter:
> 
> function initialFunction(x){
>     alert(x);            ^
            ^--------------'
>     setInterval( function(x){
>        alert(x);          ^
               ^------------'
>     }, 5000);
> }

This does not work, because in the context of the function (referred by 
`repeatingStuff'), `x' is bound to the inner function's argument `x' (which 
is not passed a useful value from the DOM implementation anyway) and not to 
that of the inner function's definition context.  Please test before you 
post, or clearly mark code as untested.

> You should pass a function to setIntervall/Timeout, instead of a code to
> be evaluated each time (slow & buggy).

The function code also will have to be evaluated each time.  But it is true 
that evaluating the string value as a Program is less efficient and more 
error-prone than that.
 
> Another alternative is to use bind() or other functions, to return a
> function which calls repeatingStuff with the needed parameters:
> 
> function repeatingStuff(){...}
> function initialFunction(x){
>     alert(x);
>     setInterval( repeatingStuff.bind(this, x), 5000);
> }

This works in implementations of ECMAScript 5.x or where you have a suitable 
scripting framework that emulates Function.prototype.bind(), but it is 
unnecessarily inefficient by comparison.


PointedEars
-- 
> If you get a bunch of authors […] that state the same "best practices"
> in any programming language, then you can bet who is wrong or right...
Not with javascript. Nonsense propagates like wildfire in this field.
  -- Richard Cornford, comp.lang.javascript, 2011-11-14

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#11709

Thomas 'PointedEars' Lahn schrieb:
> Andreas Bergmaier wrote:
>> Tuxedo schrieb:
>>> How can a simple string parameter be passed between two functions while
>>> inside a setInterval call?
>>
>> function initialFunction(x){
>>      alert(x);            ^
>              ^--------------'
>>      setInterval( function(x){
>>         alert(x);          ^
>                 ^------------'
>>      }, 5000);
>> }
>
> This does not work, because in the context of the function (referred by
> `repeatingStuff'), `x' is bound to the inner function's argument `x' (which
> is not passed a useful value from the DOM implementation anyway) and not to
> that of the inner function's definition context.

I'm sorry, I forgot the essential thing when copying the example code :-(
@Tuxedo: The thing is to have only one variable "x". The code should be

function initialFunction(x){
     alert(x);
     setInterval( function(){
        alert(x);
     }, 5000);
}

>> Another alternative is to use bind() or other functions, to return a
>> function which calls repeatingStuff with the needed parameters
>
> This works in implementations of ECMAScript 5.x or where you have a suitable
> scripting framework that emulates Function.prototype.bind(), but it is
> unnecessarily inefficient by comparison.

Is it? Unnecessarily in this case, yes, but if you have defined 
"repeatingStuff" elsewhere it is imho much more elegant than coding

var x;
setInterval( function(){
    doRepeatingStuffWith(x);
}, 5000);

  Bergi

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#11710

Andreas Bergmaier wrote:

> Thomas 'PointedEars' Lahn schrieb:
>> Andreas Bergmaier wrote:
>>> Another alternative is to use bind() or other functions, to return a
>>> function which calls repeatingStuff with the needed parameters
>>
>> This works in implementations of ECMAScript 5.x or where you have a
>> suitable scripting framework that emulates Function.prototype.bind(), but
>> it is unnecessarily inefficient by comparison.
> 
> Is it? Unnecessarily in this case, yes, but if you have defined
> "repeatingStuff" elsewhere it is imho much more elegant than coding
> 
> var x;
> setInterval( function(){
>     doRepeatingStuffWith(x);
> }, 5000);

That is not even equivalent in the first place.  Clearly you do not 
understand bind().  Please refrain from recommending it until you do.


PointedEars
-- 
When all you know is jQuery, every problem looks $(olvable).

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#11715

Thomas 'PointedEars' Lahn schrieb:
> Andreas Bergmaier wrote:
>> Thomas 'PointedEars' Lahn schrieb:
>>> Andreas Bergmaier wrote:
>>>> Another alternative is to use bind() or other functions, to return a
>>>> function which calls repeatingStuff with the needed parameters
>>>
>>> This works in implementations of ECMAScript 5.x or where you have a
>>> suitable scripting framework that emulates Function.prototype.bind(), but
>>> it is unnecessarily inefficient by comparison.
>>
>> Is it? Unnecessarily in this case, yes, but if you have defined
>> "repeatingStuff" elsewhere it is imho much more elegant than coding
>>
>> var x;
>> setInterval( function(){
>>      doRepeatingStuffWith(x);
>> }, 5000);
>
> That is not even equivalent in the first place.  Clearly you do not
> understand bind().  Please refrain from recommending it until you do.

I do, and I never said it was to be equivalent. Of course bind() needs a 
context to set, dereferences x, and builds a new function. That even 
could be useful (I'm not sure what the OP needs), so why shouldn't I 
mention it as an alternative?

  Bergi

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#11718 — Re: Simple parameter passing within a setInterval() call?

Andreas Bergmaier wrote:

[...]

> @Tuxedo: The thing is to have only one variable "x". The code should be
> 
> function initialFunction(x){
>      alert(x);
>      setInterval( function(){
>         alert(x);
>      }, 5000);
> }

Thanks - works great! Much better than my quoted parameters as in 
Stuff("' + x + '")',5000 etc.

Tuxedo

[..]

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