Birtviewer Unable to get property 'style' of undefined or null reference

问题

I have created the following javascript function to hide or show charts and then calling it from a text item.

function showhidetab(showflag,bookmark, heightval, tab)
{
    if (tab == 'overview')
    {
            document.getElementById('overgrid').style.visibility="visible";
            document.getElementById('overgrid').style.display = "block"
            document.getElementById('overgrid').style.height= '6in';


    }

    else
    {
            document.getElementById('overgrid').style.visibility="hidden";
            document.getElementById('overgrid').style.display = "none"
            document.getElementById('overgrid').style.height='0px';


    }

}

This function is working when I run it as html or in preview. However, When I deploy the report on birtviewer view it on IE/safari etc, I get the following error

SCRIPT5007: Unable to get property 'style' of undefined or null reference

Can someone please tell me why is the report behaving differently when run through browsers and on Birtviewer/apache

Regards

Syed

来源：https://stackoverflow.com/questions/23593812/birtviewer-unable-to-get-property-style-of-undefined-or-null-reference