chart js x axis data bar

new Chart(document.getElementById("mixed-chart"), {
    type: 'bar',
    data: {
      labels: ["1900", "1950", "1999", "2050"],
      datasets: [{
          label: "Europe",
          type: "line",
          borderColor: "#8e5ea2",
          data: [408,547,675,734],
          fill: false
        }, {
          label: "Africa",
          type: "line",
          borderColor: "#3e95cd",
          data: [133,221,783,2478],
          fill: false
        }, {
          label: "Europe",
          type: "bar",
          backgroundColor: "rgba(0,0,0,0.2)",
          data: [408,547,675,734],
        }, {
          label: "Africa",
          type: "bar",
          backgroundColor: "rgba(0,0,0,0.2)",
          backgroundColorHover: "#3e95cd",
          data: [133,221,783,2478]
        }
      ]
    },
    options: {
      title: {
        display: true,
        text: 'Population growth (millions): Europe & Africa'
      },
      legend: { display: false }
    }
});

data: {
    datasets: [{
        barPercentage: 0.5,
        barThickness: 6,
        maxBarThickness: 8,
        minBarLength: 2,
        data: [10, 20, 30, 40, 50, 60, 70]
    }]
};