Other than those defined variables, showVars() also checks the availabilities of document.body and a <div> that is placed in the end of the <body> (#3).
The result shows some interesting features:
-- Retrieving a tag from inside <body> section by document.getElementById() works even before the document starts loading (#1);
-- document.body is available for javascript right after the loading enters <body> tag (#2)-- doesn't have to wait until the entire loading process is completed;
-- A javascript variable V defined with a <script> tag that is inserted into <body> section is availabe only to those javascript code AFTER V is defined;
-- A javascript in body.onload (<body onload="??">) is executed after all elements are loaded, so it can access all of the variables defined anywhere in the document (#7).
