Clear login's cache in Titanium webview by calling a function

i am calling gmail site webview i am able to login and logout but when i open my application again i see user name is not cleared i can i clear my webview cache

something like call beforeload webview event

webview.addActionListener("beforeload",function(){
 
///clearing all cache of loading url assuption Ti.UI.clearCache(webview.url);
 
})