1、使用getElementById方法获取绘制对象2、取得上下文getContext('2d')，这都是固定的写法3、指定填充的颜色fillStyle和绘制的颜色strokeStyle，即里面的颜色和边框的颜色4、指定线宽linewidth5、填充/绘制 fillRect/strokeRect 参数为 x,y,width,height6、若是要使其中一块透明，使用clearRect至此，绘制矩形框便暂时告一段落。
绘制圆形
现在我们来绘制圆形，这个说起绘制圆形，其实我原来用js好像写过一个，这里也贴出来看看：
复制代码
我是纯js画的圆
<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>
<html xmlns=”http://www.w3.org/1999/xhtml”>
<head>
<title></title>
<style type=”text/css”>
div
{
position: absolute;
width: 1px;
height: 1px;
line-height: 1px;
}
</style>
<script src=”http://www.cnblogs.com/jquery-1.7.1.js” type=”text/javascript”></script>
<script type=”text/javascript”>
//x2 + y2 = r2;
$(document).ready(function () {
//先画x，y
var box = $(‘#box’);
var NUM = 200;
var R = NUM / 2;
var RR = R * R;
for (var i = 0; i <= NUM; i = i + 6) {
//var divX = $(‘<div style=”left:’ + i + ‘px;top:’ + R + ‘px;”>*</div>’)
// var divY = $(‘<div style=”top:’ + i + ‘px;left:’ + R + ‘px;”>*</div>’)
var ti = i;
//sqrt(x)
if (ti > R) {
ti = ti – R;
var ty = Math.sqrt((RR – ti * ti));
var y = $(‘<div style=”left:’ + (R – ty) + ‘px;top:’ + i + ‘px;”>*</div>’)
var y1 = $(‘<div style=”left:’ + (R + ty) + ‘px;top:’ + i + ‘px;”>*</div>’)
box.append(y);
box.append(y1);
} else if (ti < R) {
ti = R – ti;
var ty = Math.sqrt((RR – ti * ti));
var y = $(‘<div style=”left:’ + (R – ty) + ‘px;top:’ + i + ‘px;”>*</div>’)
var y1 = $(‘<div style=”left:’ + (R + ty) + ‘px;top:’ + i + ‘px;”>*</div>’)
box.append(y);
box.append(y1);
}
//box.append(divX);
//box.append(divY);
}
for (var i = 0; i <= NUM; i = i + 6) {
//var divX = $(‘<div style=”left:’ + i + ‘px;top:’ + R + ‘px;”>*</div>’)
// var divY = $(‘<div style=”top:’ + i + ‘px;left:’ + R + ‘px;”>*</div>’)
