Editable javascript chart - interactively resize bars or pie sections

I need a library or a framework plugin that can draw charts that can be modified real-time by resizing part of the chart itself. Is there such thing?

I plan to use it for adjusting the chart values. Mostly for controlling amount allocation.

For example. You have 4 hours and you have 5 distinct types of tasks. I want the user to be able to allocate time for each task and see visually what's the impact on the available time.