Easy Flags

<div style='background:silver;padding:5px'>
<canvas id='usr' width=150 height=100></canvas>
<canvas id='ans' width=150 height=100 style='display:none'></canvas>
</div>

--snippet-usr--
drawFlag(document.getElementById('usr').getContext('2d'));
(()=>{
  --snippet-ans--
  drawFlag(document.getElementById('ans').getContext('2d'));
})();
let [a,b] = ['usr','ans']
    .map(id=>document.getElementById(id))
    .map(elem=>elem.getContext('2d').getImageData(0,0,elem.width,elem.height))
let diff = a.data.map((v,i) => v===b.data[i]?1:0).reduce((acc,v)=>acc+v,0)*100/a.data.length;
let fb = document.createElement('div');
fb.innerText = `Score: ${diff.toFixed(1)}`;
document.body.appendChild(fb);

Libya

The flag of Libya, until 2011, was a simple green rectangle.

Try the program as it is given, then change it so that the green rectangle is 150 wide.

function drawFlag(ctx)
{
  ctx.fillStyle = 'green';
  ctx.fillRect(0,0,75,100);
}  

function drawFlag(ctx)
{
  ctx.fillStyle = 'green';
  ctx.fillRect(0,0,150,100);
}  

France

The flag of France is blue, white and red. The code given draws only one of the three rectangles required and it is in the wrong place.

function drawFlag(ctx)
{
  ctx.fillStyle = 'blue';
  ctx.fillRect(50,0,50,100);
}

function drawFlag(ctx)
{
  ctx.fillStyle = 'blue';
  ctx.fillRect(0,0,50,100);
  ctx.fillStyle = 'white';
  ctx.fillRect(50,0,50,100); 
  ctx.fillStyle = 'red';
  ctx.fillRect(100,0,50,100); 
}

Germany

The flag of Germany is black, red and yellow.

Only one of the three rectangles has been drawn - and that one is in the wrong place.

function drawFlag(ctx)
{
  ctx.fillStyle = 'yellow';
  ctx.fillRect(0,0,150,30);
} 

function drawFlag(ctx)
{
  ctx.fillStyle = 'black';
  ctx.fillRect(0,0,150,30);
  ctx.fillStyle = 'red';
  ctx.fillRect(0,30,150,30);
  ctx.fillStyle = 'yellow';
  ctx.fillRect(0,60,150,30);
}

Switzerland

The flag of Switzerland is red with a white cross in the center.

The background has been filled in. Use white rectangles to draw the cross.

function drawFlag(ctx)
{
  ctx.fillStyle = 'red';
  ctx.fillRect(0,0,100,100);
}

function drawFlag(ctx)
{
  ctx.fillStyle = 'red';
  ctx.fillRect(0,0,100,100);
  ctx.fillStyle = 'white';
  ctx.fillRect(10,40,80,20);
  ctx.fillRect(40,10,20,80);
}

Japan

• The flag of Japan is a red circle on a white background.
• The rectangle is 150 by 100.
• The circle is in position 45,20, width and height are 60,60.

g.fillOval(0,0,150,100) will fill an oval bounded by the whole shape. See Draw Circle

function drawFlag(ctx)
{
  ctx.fillStyle = 'white';
  ctx.fillRect(0,0,150,100);
  ctx.fillStyle = 'red';
}

function drawFlag(ctx)
{
  ctx.fillStyle = 'white';
  ctx.fillRect(0,0,150,100);
  ctx.fillStyle = 'red';
  ctx.fillOval(45,20,60,60);
}