[Solved]-Chart.js: Line chart with partial dashed line-Chart.js

One solution may be: set values of dataset(1) to null when it isn't visible. This line does not create a bezier Curve, it's the inconvenience.

Example:

var lineChartData = {
labels: ['A', 'B', 'C', 'D', 'E', 'F', 'G'],
datasets: [{
    label: "My First dataset",
    data: [, , , , 2, 3, 4],
    borderColor: '#66f',
    borderDash: [20, 30],
    pointBackgroundColor: "transparent"
},{
    label: "My First dataset",
    data: [1, 8, 3, 4, 2, , ],
    borderColor: '#66f',
    pointBackgroundColor: "transparent"
}]

};

https://jsfiddle.net/scs_3/8qqv69ot/