Add DataSet Bar Chart - Chart.JS

Since you store your chart data in a variable (called data in your code), you can do it with a simple function on a button :

$('button').click(function() {
    // You create the new dataset `Vendas` with new data and color to differentiate
    var newDataset = {
        label: "Vendas",
        backgroundColor: 'rgba(99, 255, 132, 0.2)',
        borderColor: 'rgba(99, 255, 132, 1)',
        borderWidth: 1,
        data: [10, 20, 30, 40, 50, 60, 70],
    }

    // You add the newly created dataset to the list of `data`
    data.datasets.push(newDataset);

    // You update the chart to take into account the new dataset
    myBarChart.update();
});

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You can see the full code on this jsFiddle and here is its result after a click :