Gridder - developer tool which cover page with grid for easier coding

Gridder.js

function setupCanvas() {
	var canvas = document.createElement('canvas');
	document.body.appendChild(canvas);
	canvas.width = 4000;
	canvas.height = 4000;
	canvas.id = "grid";
	canvas.style.position = "absolute";
	canvas.style.left = "0px";
	canvas.style.top = "0px";
	canvas.style.overflow = 'hidden';
}

function drawGrid(x_dist, y_dist, color) {
	var a_canvas = document.getElementById("grid");
	var a_context = a_canvas.getContext("2d");
	for (var x = 0.5; x < 1500; x += x_dist) {
  		a_context.moveTo(x, 0);
  		a_context.lineTo(x, 3000);
	}

	for (var y = 0.5; y < 1500; y += y_dist) {
  		a_context.moveTo(0, y);
  		a_context.lineTo(3000, y);
	}

	a_context.strokeStyle = color;
	a_context.stroke();
}

window.onload = function() {
	// Set it up here
	var x_dist = 20;
	var y_dist = 20;
	var color = "#00ffff";

	// Let it run
	setupCanvas();
	drawGrid(x_dist, y_dist, color);
}