Now that our AJAX calls are succeeding, let's start building our app. From here on out, it's all basic JavaScript and D3. Note that everything we'll write for the rest of this lesson is done within the success callback of our AJAX request. In production, we might want to move this code elsewhere, but for now this is easier for learning. Let's create some rectangles for our bar graph. The bottom of app.js (the callback to the AJAX request) should now look as follows:

d3.json('data.json').then(function(data){
    d3.select('svg').selectAll('rect')
        .data(data)
        .enter()
        .append('rect');
});

Our Elements tab in our dev tools should look something like this: