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#1
May 1st, 2008, 07:41 PM
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XMLHttpRequest onreadstatechange callback with parameter
Hey,
I can specify a callback function for the XMLHttpRequest onreadstatechange like so; Code:
function callback()
{
...
}
function request()
{
...
http.onreadystatechange = callback;
...
}
However, I want to pass a parameter to the callback function and simply doing this doesn't appear to work: Code:
function callback( param )
{
...
}
function request( param )
{
...
http.onreadystatechange = callback( param );
...
}
Am I just missing a trick somewhere, or is this not possible? Thanks for your time.
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#2
May 1st, 2008, 07:56 PM
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The second version calls the function and assigns its return value as the event handler.
You can do this by using an anonymous function. Code:
function callback( param )
{
...
}
function request( param )
{
...
http.onreadystatechange = function(){
callback( param );
}
...
}
__________________
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#5
May 5th, 2008, 03:40 PM
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When you call a function, it returns a value. You specify that value by using a return statement with a value. For example, this function's return value is the string "Hello World".
Code:
function myFunc(){return "Hello World";}
If the function completes without encountering a return statement or encounters one without an associated value, then the function will return undefined. A function is called by including the "()" (with or without passing any arguments) after the function name (or some other reference to it). You can also call a function with the apply() or call() methods (keep in mind that IE versions before 5.5 don't support those natively). Does that sufficiently explain it for you?
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