[HTML5/Javascript] Couple questions, particularly dealing with Canvas

[FalseProphet]

Hi, I am pretty new to Javascript and would like to play with the Canvas and I have a couple questions.

First off, how do I record frame rate or operations per second properly? In my current code I only get around 170 FPS with nothing on the canvas and the canvas being  default size:

// GetElapsedMilliseconds = Function() { var time = new Date(); return time.getMilliseconds(); }
if (GetElapsedMilliseconds() - oldTime >=1000) {
	OPS = count;
	count = 0;
	oldTime = GetElapsedMilliseconds();
}

++count;
loop = setTimeout('Main()', 1);

 

Another thing, am I doing Javascript's OOP implementation correctly?

myscene = new _Context("thecanvas");
function _Context(id) {

/*

	description:	Retrieve the canvas context by id, if it can't throw 
					an error and reason.

*/

if (document.getElementById(id)) {
		this.canvas = document.getElementById(id).getContext("2d");
} else {
	alert("Error\nUnable to find element ID: " + id);
	return null;
}


this.DrawText = function(x, y, string, size, font, color) { // draw some text inside of the canvas

	/*

		description:	Draw text to the canvas.

	*/

	this.canvas.font = size + "px " + font;
	this.canvas.fillStyle = color;
	this.canvas.fillText(string, x, y);

}
}

[Alex]

170FPS is probably right. Browsers throttle timers to a minimum limit, so your setTimeout('Main()', 1) isn't being called every millisecond. Each browser is different, I think for chrome the minimum is 3ms and for FF it's 5ms or something like that, but don't quote me on it.

[haku]

170fps may be overboard. I believe TV runs around 24 frames per second, and according to wikipedia, video games are thought to be acceptable at 30-60fps, though some go over 100.