Clear canvas path

I have been trying to clear paths made with canvas on a map. The map has 10 paths that are started on the click event. I want to be able to reset the map with no path when all the path have been seen.

I tried:

var myCanvas = $('<canvas />');

myCanvas.attr("width", 780);

myCanvas.attr("height", 470);

btn = sym.$("btn");

index = -1;

btn.click(function(){

  index++;

  sym.play("p" + index);

  if (index>=7){

  index=-1;

  ctx0.clearRect(0,0,myCanvas[0].width,myCanvas[0].height);

  ctx1.clearRect(0,0,myCanvas[0].width,myCanvas[0].height);

  ctx6.clearRect(0,0,myCanvas[0].width,myCanvas[0].height);

  ctx2.clearRect(0,0,myCanvas[0].width,myCanvas[0].height);

  ctx3.clearRect(0,0,myCanvas[0].width,myCanvas[0].height);

  ctx4.clearRect(0,0,myCanvas[0].width,myCanvas[0].height);

  ctx5.clearRect(0,0,myCanvas[0].width,myCanvas[0].height);

  }

});

but it does not clear anything.