some observation on using document.getElementById

Question

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For the 2 lines of code below after clicking a RETURN or TAB key:

JavaScript

document.getElementById('<%=txtPID.ClientID%>').focus();  //#1
document.getElementById('<%=txtPID%>').focus();           //#2

For #1, I can retrieve the control's values, but the control is not focus, and the highlight point flashes on the next control.
For #2, I got

JavaScript

JavaScript runtime error: Unable to get property 'focus' of undefined or null reference

What's wrong in my coding? Thanks.

Posted 17-Aug-15 5:54am

s yu

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Comments

Sergey Alexandrovich Kryukov 17-Aug-15 12:08pm

And..?
Read page source on client side, and you will see.
—SA

s yu 17-Aug-15 12:16pm

Thanks for your response. However, I am not clear your meaning. E.g. how to read page source on client side? For #1, it moves to another control rather than still focus on the current control; for #2, it pops up error. Could you hint me how to 'Read page source on client side'? Thanks again.

Zoltán Zörgő 17-Aug-15 13:26pm

Just a question: why do you want to focus the element to read any property of it?

Sergey Alexandrovich Kryukov 17-Aug-15 13:51pm

The argument of this function is the value of the attribute "id" of any HTML element. ClientID is one of the way to calculate this value on server side.
—SA

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