In app.js, let's create an array of run objects, I am storing the date as a string on purpose also, it's important that this is an array of objects, to work with D3). Here's what your app.js code should look like so far:
var WIDTH = 800; var HEIGHT = 600; var runs = [ { id: 1, date: 'October 1, 2017 at 4:00PM', distance: 5.2 }, { id: 2, date: 'October 2, 2017 at 5:00PM', distance: 7.0725 }, { id: 3, date: 'October 3, 2017 at 6:00PM', distance: 8.7 } ]; d3.select('svg') .style('width', WIDTH) .style('height', HEIGHT);