Chart.js: Dynamic Changing of Chart Type (Line to Bar as Example)

Question

I am trying to hot swap chart types based on select box changes. If data needs to be updated, it changes.

So for example, on page load I create a chart like this:

var config = {
     type: 'line',
     data: {
        labels: this.labels,
        datasets: [{
            label: 'Some Label',
            data: this.values
        }]
     },
     options: {
         responsive: true
     }
}
var context = document.getElementById('canvas').getContext('2d');
window.mychart = new Chart(context, config);

But then I change the combo box to a bar chart. I have tested the data with bar chart on page load, and it worked great.

Here's how I am trying to change the chart.

window.mychart.destroy();

// chartType = 'bar'
config.type = chartType;

var context = document.getElementById('canvas').getContext('2d');
window.mychart = new Chart(context, config);

window.mychart.update();
window.mychart.render();

But nothing happens. The line chart remains. How can I dynamically change the chart type? (Even if it means destroying & re-creating the chart canvas).

UPDATE

Note it looks like it is actually destroying the chart, but keeps redrawing a line chart, even though I do console.log(config.type); and it returns bar, not line

Answer 1

The Fix

• Destroy the old chart (to remove event listeners and clear the canvas)
• Make a deep copy of the config object
• Change the type of the copy
• Pass the copy instead of the original object.

Here is a working jsfiddle example

Example Overview:

var temp = jQuery.extend(true, {}, config);
temp.type = 'bar'; // The new chart type
myChart = new Chart(ctx, temp);

NOTE: Using version 2.0.1 of Chart.js

Why this works

Chart.js modifies the config object you pass in. Because of that you can not just change 'config.type'. You could go into the modified object and change everything to the type you want, but it is much easier to just save the original config object.