Canvas.toDataURL（）未捕获TypeError：undefined不是函数

Question

I'm using a plugin called html2canvas to convert some html on my page into a canvas element. I then want to save that canvas as an image. Unfortunately I keep encountering the error in the title. I have tried with different variable names, with different html, etc. But keep encountering the same error. Here is my code (triggered on a button click):

JS

function generate(){
        html2canvas($('#b2_1'), {
            onrendered: function(canvas) {
                canvas.setAttribute("id", "canvas");
                document.body.appendChild(canvas);
            }
        });//this all works, the canvas appears as expected

        var myCanvas = $(document).find('#canvas');
        myCanvas.css("margin-left", "50px");//this was to test I was selecting the right element, the canvas moves
        var myImg = myCanvas.toDataURL();//code breaks here
    }

Answer 1

Ok, I found my problem was I was trying to call toDataURL() on my jQuery object rather than my canvas element. To fix this I used .get(0) . Full code below:

function generate(){
        html2canvas($('#b2_1'), {
            onrendered: function(canvas) {
                canvas.setAttribute("id", "canvas");
                document.body.appendChild(canvas);
            }
        });//this all works, the canvas appears as expected

        var myCanvas = $(document).find('#canvas');
        myCanvas.css("margin-left", "50px");
        var myImg = myCanvas.get(0).toDataURL();//have to get the canvas element from the jquery object
    }