异步将新数据加载到d3图表

I'm building a sort of timeline tool using d3.js that can be zoomed and paged forward and back within a set time period. I have my axis transitioning perfectly but I can't seem to get my data to reload. The idea is that the zoom level defines a moving window, for example 1 hour that the user moves backwards and forwards over a period of a few days. Every time they do so a call is made to fetch the data for that hour.I'm building a sort of timeline tool using d3.j