perf-test.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Title</title>
    <script type="text/javascript">
      function test() {
        function tst(fb32, destOffset, numPixels) {
          var black = 0xff000000;
          while (numPixels--) {
            fb32[destOffset++] = black;
          }
        }

        var fb32 = new Uint32Array(1024);
        var reps = 500000;
        var start = Date.now();
        for (var i = 0; i < reps; ++i) tst(fb32, 0, 16);
        var end = Date.now();
        var result = "Took " + (end - start) + "ms to do " + reps + " 16 32-bit clears";
        console.log(result);
        document.getElementById("result").innerHTML = result;
      }
    </script>
  </head>
  <body onload="test()">
    <h2>Test</h2>
    <div><span id="result">Running test....</span></div>
  </body>
</html>