We have just released v1.9.6 Beta with Methods & Properties, which allows you to export chart as image, print chart, programmatically access internally calculated values, etc. Please refer to the release blog for more information.
In canvasjs.min.js or canvasjs.js all chart initialized variables can be reffered using chart.options. So, here you can use
chart.options.data.type to get assigned chart type of first dataSeries.