HTML canvas - drawing disappear on resizing

Question

I have created a basic shape in HTML canvas element which works fine.

The problem occurs when I resize the canvas, all the drawing in the canvas disappears. Is this

Answer 1

I had the same problem when I had to resize the canvas to adjust it to the screen. But I solved it with this code:

var c = document.getElementById('canvas');
ctx = c.getContext('2d');
ctx.fillRect(0,0,20,20);
// Save canvas settings
ctx.save();
// Save canvas context
var dataURL = c.toDataURL('image/jpeg');
// Resize canvas
c.width = 50;
c.height = 50;
// Restore canvas context
var img = document.createElement('img');
img.src = dataURL;
img.onload=function(){
  ctx.drawImage(img,20,20);
}
// Restote canvas settings
ctx.restore();