C3.js using json data to populate x axis

c3.js

//http://jsfiddle.net/r0hydxpb/2/

var chart = c3.generate({
        data:{
              json:[
                 {"key":2000,"value":100},{"key":2001,"value":200},
                 {"key":2003,"value":300},{"key":2004,"value":400},
                 {"key":2005,"value":500},{"key":2006,"value":600},
                 {"key":2007,"value":700}
              ],
              keys:{
                  x: 'key',
                  value:['value']
              }
    },
    axis: {
          x: {
            x:['key'],
            type: "category"
          }
        }
});

//alert(chart.data('key')[0]);
console.log(chart.data('key')[0].values[3].value)
console.log(chart.data('value')[0].values[3].value)