iTunes backup also WhatsApp chats? a friend of mine has an iPhone 3GS and is swtiching to an iPhone 4S.
Now, she's tried to backup all her WhatsApp chats using the WhatsApp backup, but it gets stuck. So I'm thinking whether iTunes backup may do that too.

I know iTunes backups everything on your iPhone, so if those chats are on her iPhone it should work, isn't it?

So should I connect the iPhone to a PC/Mac and start an iTunes backup? Would that work to get the chats back when I'll restore the backup in the 'new' iPhone?
When WhatsApp backup to iCloud gets stuck

It's a 'bit late' but I recently experienced a similar problem to the one above, date June 2016.
For people like me who - for some reason - still have to change their iPhone 4 to 6s in 2017, you can bump into the problem that Whatsapp gets stuck while backing up on iCloud. It took me a while but I solved it eventually with the following steps:


Stop Whatsapp from being stuck: Settings > iCloud > switch off
Document Data &amp; WhatsApp
Delete your current Apple ID account on your iPhone 4 Create a new free Apple ID ON YOUR IPHONE 4: Settings > iTunes en Appstore > Create new free Apple ID 
Settings > iCloud > switch on Document Data &amp; WhatsApp Go to Whatsapp > Create backup 
On iPhone 6 log off with current Apple ID (and make sure you log off
with iCloud AND iTunes) and log in with the new ID you created on old
iPhone 4 
On iPhone 6 install Whatsapp from Appstore and import the backup from iCloud


iPhone 4 (iOs 7) has a problem with updated iCloud (Drive) but via this bypass you can do the trick.