Vega: A Visualization Grammar
What are the best for D3-based visualization/charting libraries when it comes to being high customizable, styleable, and performant?  There are dozens of them, but with some research the most interesting ones seem to be:* Vega - Talked about in this thread* nvd3 - Meant to work in similar style as D3, supports extension.  Seems popular* Epoch - Real-time charts are purpose-built to be performant and low-overhead. Limited number of visualization types* D4	- Extends D3 instead of wrapping it. Separation of data from view* C3js - Easier API.  extendable.* rickshaw - Mainly for time series data.  Supports extensions. Works in similar style as D3.