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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>Practice JavaScript by drawing</title>
</head>
<body>
  <canvas id="myCanvas" height="300" width="450" style="border: 1px solid black"></canvas>
<script id="jsbin-javascript">
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

var cH = canvas.height;
var cW = canvas.width;

var y = 0;
var x = 0;
var number = 1;
var col = prompt('Oszlopok száma?');
var row = prompt('Sorok száma?');

function drawCheckeredPattern(row,col){
 for (var k = 1; k<=row; k++) {
  for (var i = 1; i <=col; i++){
    if (number % 2 === 0) {
      context.fillStyle = 'white';
      context.fillRect(y,x,50,50);
      y = y +50;
    }else{
      context.fillStyle = 'black';
      context.fillRect(y,x,50,50);
      y = y +50;
    }
  number = number+1;
}
  y = 0;
  x = x+50;
  number = number+1;
}
};

drawCheckeredPattern(row,col);
</script>


<script id="jsbin-source-javascript" type="text/javascript">var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

var cH = canvas.height;
var cW = canvas.width;

var y = 0;
var x = 0;
var number = 1;
var col = prompt('Oszlopok száma?');
var row = prompt('Sorok száma?');

function drawCheckeredPattern(row,col){
 for (var k = 1; k<=row; k++) {
  for (var i = 1; i <=col; i++){
    if (number % 2 === 0) {
      context.fillStyle = 'white';
      context.fillRect(y,x,50,50);
      y = y +50;
    }else{
      context.fillStyle = 'black';
      context.fillRect(y,x,50,50);
      y = y +50;
    }
  number = number+1;
}
  y = 0;
  x = x+50;
  number = number+1;
}
};

drawCheckeredPattern(row,col);</script></body>
</html>