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html - HTML5, JavaScript and drawing multiple rectangles in a canvas

Why won't my multiple rectangles draw in the canvas?

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title></title>
    <script src="Scripts/jquery-1.9.1.min.js"></script>
  </head>
  <body>
    <canvas id="myCanvas" width="500" height="500" style="border:1px solid red">
      <p>Your browser doesn't support canvas.</p>
    </canvas>
  </body>
</html>

<script type ="text/javascript">  
  function Shape(x, y, w, h, fill) {
    this.x = x;
    this.y = y;
    this.w = w;
    this.h = h;
    this.fill = fill;
  }

  // get canvas element.
  var elem = document.getElementById('myCanvas');

  // check if context exist
  if (elem.getContext) {

    var myRect = [];

    myRect.push(new Shape(10, 0, 25, 25, "#333"))
    myRect.push(new Shape(0, 40, 39, 25, "#333"))
    myRect.push(new Shape(0, 80, 100, 25, "#333"))

    context = elem.getContext('2d');
    for (i in myRect) {

      //console.log(x);

      context.fillRect(i.x, i.y, i.w, i.h)
    }
    //// x, y, width, height
    //context.fillRect(0, 0, 50, 50);

    //// x, y, width, height      
    //context.fillRect(75, 0, 50, 50);
  }
</script>  

Thanks for help.

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1 Reply

0 votes
by (71.8m points)

Ok, so you were almost there. When you iterate round your array of rectangles, you are iterating over the array key not the objects themselves (see How to Loop through plain JavaScript object with objects as members?). Plus, as @jimjimmy1995 pointed out, you need to set the fill using .fillStyle as .fillRect does not have a fill parameter.

This code will work:

function Shape(x, y, w, h, fill) {
    this.x = x;
    this.y = y;
    this.w = w;
    this.h = h;
    this.fill = fill;
}

// get canvas element.
var elem = document.getElementById('myCanvas');

// check if context exist
if (elem.getContext) {

    var myRect = [];

    myRect.push(new Shape(10, 0, 25, 25, "#333"));
    myRect.push(new Shape(0, 40, 39, 25, "#333"));
    myRect.push(new Shape(0, 80, 100, 25, "#333"));

    context = elem.getContext('2d');
    for (var i in myRect) {
        oRec = myRect[i];
        context.fillStyle = oRec.fill;
        context.fillRect(oRec.x, oRec.y, oRec.w, oRec.h);

    }

}

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