Flags with Repeats
<div style='background:silver;padding:5px'> <canvas id='usr' width=--snippet-w-- height=--snippet-h--></canvas> <canvas id='ans' width=--snippet-w-- height=--snippet-h-- 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: ${diff.toFixed(1)}`;
document.body.appendChild(fb);
fetch(`/reportProgress.php?uid=--snippet-uid--&qid=--snippet-qid--&score=${diff}`);
We can repeat a statement or block of statements with a for loop. The classic for loop takes the following form:
for(let i = 0; i< 10; i++){
console.log(i);
}
The body of the loop runs 10 times, control variable i takes every value 0,1,2..9 in turn. We can use the value of i inside the loop if required.
Bahrain
The flag of Bahrain has a five irregular pentagons on a red background.
Each pentagon can be represented by five points such as (0,0), (64,0) (100,15) (64,31) and (0,31).
function drawFlag(ctx)
{
ctx.fillStyle = 'red';
ctx.fillRect(0,0,250,155);
for(let i=0;i<5;i++){
ctx.beginPath();
ctx.moveTo(0,0);
ctx.lineTo(64,0);
ctx.lineTo(100,15);
ctx.lineTo(64,31);
ctx.lineTo(0,31);
ctx.fill();
}
}
function star(ctx)
{
ctx.beginPath();
[ [ 0,-50],[11,-16],[48,-16],[18,6],[30,41],
[ 0,18],[-30,41],[-18,6],[-48,-16],[-11,-16]
].forEach((xy) => ctx.lineTo(xy[0],xy[1]));
ctx.fill();
}
function drawFlag(ctx)
{
ctx.fillStyle = 'red';
ctx.fillRect(0,0,200,150);
ctx.translate(100,75);
ctx.fillStyle='yellow';
star(ctx);
}
function star(ctx)
{
ctx.beginPath();
[ [ 0,-50],[11,-16],[48,-16],[18,6],[30,41],
[ 0,18],[-30,41],[-18,6],[-48,-16],[-11,-16]
].forEach((xy) => ctx.lineTo(xy[0],xy[1]));
ctx.fill();
}
