When I recently switched to iPhone from my Android phone and installed WhatsApp into it. I was wondering whether the WhatsApp for iOS has smileys or not. And to my good it do has smileys. But in order to use it you need to activate Emoji keyboard in your iPhone Settings.
To Activate Emoji Keyboard in your iPhone, goto Settings > General > Keyboard > Keyboards > Add New Keyboard > Select Emoji.
Now go back to WhatsApp and on Keyboard, click on the Globe shaped button, second to left, in the last bottom row. And it will change your keyboard to Emoji. You can now add your favourite smiley to your chats.