IE 8中的元素始终为空

I have the following code:

我有以下代码：

 if (document.querySelectorAll('[id$=":maindiv:usernametext::content"]')[0].value == null || document.querySelectorAll('[id$="maindiv:usernametext::content"]')[0].value.trim() == "") {
        console.log("maindiv:usernametext::content IS EMPTY !!!);
    }
 if (doc