javascript - How can I access the canvas element without an id? -

using casperjs, i'm trying testing on canvas, grabbing , using canvas.todataurl();. however, canvas not have id, code looks this:

<div id= 'derp' ...> <canvas ...> </canvas> </div> 

can still canvas using

var canvas = document.getelementbyid(????); 

or there better way of grabbing canvas?

you can use css selectors:

document.queryselector('#derp canvas')