c3js stacked bar chart

HTML

<script src="https://rawgit.com/masayuki0812/c3/master/c3.js"></script>
<link rel="stylesheet" href="https://rawgit.com/masayuki0812/c3/master/c3.css">
<div id="chart"></div>

JavaScript

var chart = c3.generate({
bindto: "#chart",
    data: {
        x : 'x',
        columns: [
            ['x', 'AAAA', 'BBBB', 'CCCC', 'DDDD','EEEE'],
            ['Successful', 980, 439, 274, 390, 3],
            ['Failed', 289, 114, 36, 53, 386]
        ],
        groups: [
            ['Successful', 'Failed']
        ],
        type: 'bar'
    },
    axis: {
        x: {
            type: 'category' // this needed to load string x value
        }
    }
});