Prototype, subfunctions, and variable scope

[Nutter]

Say I've got the following sort of code to do an Ajax call with the Prototype library.

function myFunction(url, myVariable)
{
new Ajax.Request(url, {method:'post', parameters="value=somevalue",
onSuccess:function()
{
alert(myVariable); 
});
}

I want to be able to use the myVariable variable that's part of the function line in the onSuccess function, but it seems that the scope doesn't work. When I try to use it, the variable is undefined.

Is there a way to use it? I'm sure I'm missing something easy.

[Fotiman]

I haven't really looked that closely but it appears as though you're missing a closing }.

function myFunction(url, myVariable) 
{ 
  new Ajax.Request 
  ( 
    url, 
    { 
      method:'post',  
      parameters="value=somevalue", 
      onSuccess:function() 
      { 
        alert(myVariable); 
      } 
  ); 
} 

Should be:

function myFunction(url, myVariable) 
{ 
  new Ajax.Request 
  ( 
    url, 
    { 
      method:'post',  
      parameters="value=somevalue", 
      onSuccess:function() 
      { 
        alert(myVariable); 
      } 
    } 
  ); 
} 

Don't know if that's your problem or not... no time to look close right now.

[Nutter]

I probably am missing a bracket in what I put here, but the real function (a much longer version than what I typed here) works. It just can't get the value of myVariable. What I've done for now is pass the value of myVariable to the PHP script that then sends it back as part of the return string. Seems like an inefficient way to do it, but it works for now.

[gergoe]

This particular topic is not clear to me either (how variable scope works in such a case, when nameless functions are involved for example), but I have done a quick test and for me it worked fine, I defined a nameless function within an another one (well, actually it become a sort of a class), and I could call it properly as long as the (second) function was defined inside the (first) function. So either it is a browser incompatibility issue, or the library you are using does something which makes it go wrong. To go around the problem you could save your variable into an another scope, for example to the window? Not a nice solution, but would definitely make it work :-)

[Nutter]

How would I save it into another scope? While that may be a messy solution, it's still better than what I've got working now.

And thank you for calling it a "nameless" function. I've been looking for information but didn't know that term so I was having a hard time finding anything.

[edited by: Nutter at 6:38 pm (utc) on Jan. 14, 2008]

[mehh]

to save to another scope just use

window.myVar

. That should be able to be referenced to anywere.

I think your code is failing because of a syntax error though

function myFunction(url, myVariable)  
{  
 new Ajax.Request  
 (  
 url,  
 {  
  method:'post',  
  parameters="value=somevalue",// JSON string so = isn't valid 
  onSuccess:function()  
  {  
  alert(myVariable);  
  }  
 }  
 );  
}

try:

function myFunction(url, myVariable) 
{ 
 new Ajax.Request 
 ( 
 url,
 { 
  method:'post', 
  parameters:'value=somevalue', 
  onSuccess:function() 
  { 
  alert(myVariable); 
  } 
 } 
 ); 
} 

Also if your interested in "nameless" functions they may also be referfed anonymous functions.

Quick note on scope

class.prototype={
 hello:"hi" //hello belongs to class.prototype
 foo:function (){
 var bar="foo" //bar belongs to class.prototype.foo
 global // variable not defined in class.prototype.foo assumed to be a global
 this // refers to class.prototype or an object constructed by new class();
 }
}

[Fotiman]

And thank you for calling it a "nameless" function. I've been looking for information but didn't know that term so I was having a hard time finding anything.

The actual term is "anonymous function".
Edit: I see mehh already mentioned this. Should have read further. :-)

[edited by: Fotiman at 5:00 pm (utc) on Jan. 15, 2008]