I created a grocery app, which was a good lesson in UX and good jQuery practice.
I included an Add button, but I also wanted users to be able to add by pressing the Enter key, so I learned how to do that. In fact, I think that submitting something by pressing Enter should always be an alternative to clicking an actual Submit button.
Personally, I love checklists, but it's well-organized checklists that get me really excited. If I have a list of items and some are checked off, I don't want them to be interspersed with my unchecked items. So I made sure that when each item is checked off on my grocery app, it is automatically moved to the bottom of the list. If you make a mistake and accidentally check something, unchecking it moves it back to the top of the list.
Another feature I thought about was the ability to delete individual items if they were added on by accident. I found a trash icon, which I included with each list item, so individual items could be trashed.
Lastly, I wanted a safeguard in case I clicked "Clear items already bought" by accident (if you haven't realized by now, I'm very accident-prone). Once that button is clicked, a pop-up appears asking if you're sure you want to delete those items.
Twitter Bootstrap, Sublime 2
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