XWidgetSoft Forum

Using Javascript, I have a loop that modifies the Attributes of some objects, how is it possible to check if the object exists before applying changes ?

I have tried several methods to test if the object exist, including -
if (typeof objectname == "undefined")
if (null == objectname)
if ("undefined" == typeof(objectname)

But any reference to an object that does not exist result in a "runtime error object does not exist"
Can anyone assist ?

you can input all objects you want to change into array.

Your only error was using double quotes. Use single quotes. And typeof is a method it should be declared as typeof(object)

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Hi qiancang,
I am not sure what you mean by I still want to check they exist before proceeding.

Hi digigamer
Modified code as you suggested, now the line
if(typeof(mybogusobject) != 'undefined')
returns "runtime error mybogusobject is undefined" when mybogusobject does not exist.
if mybogusobject does exist it works OK.

Any ideas ?

Thank you both very much for your replies

That should not happen... As of my understanding on JScript.
Well here's another way.
You can enclose in a try-catch block too. But before that please run this test widget.
It includes all the procedures used in JS that to detect the validity of an object. Please go through the code-behind.

Run the test. If it is successful it will write success. If any error is thrown, it will show error. In this case I'll assume that your script engine and/or some other code has a problem, coz that's the only way to test it. Try running my code and say.

SUGGESTION: A good program (here widget) never manipulates on non existent, uninitialized or nulled objects. I wonder what's your requirement. Looking forward for your widget to complete...

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Life is a myriad game... Just play it!

Thank you digigamer
I have already enclosed it in a try catch block to skip the error but as you suggested this is not a good solution.
Your test widget works OK returning "Obj Doesnot exist"

I have modified the script to only address objects that already exist.
Thanks again for you help,