<body onload="drawOval(300,300,100,80)">
<script type="text/javascript" language="javascript">
function drawOval(x, y, a, b){
if(arguments.length == 3) {
return drawOval(x, y, a, a);
}
var i, j;
var tpos = [];
var x1, x2, y1, y2;
var html = "";
for(i = 0; i <= a; i++){
j = Math.floor(Math.sqrt(b*b - b*b*i*i/(a*a))+0.5);
x1 = i+x;
x2 = -i+x;
y1 = j+y;
y2 = -j+y;
if(!tpos[x1*1000+y1])
{
drawPos(x1,y1);
drawPos(x1,y2);
drawPos(x2,y1);
drawPos(x2,y2);
tpos[x1*1000+y1] = true;
}
}
for(i = 0; i <= b; i++)
{
j = Math.floor(Math.sqrt(a*a - a*a*i*i/(b*b))+0.5);
x1 = j+x;
x2 = -j+x;
y1 = i+y;
y2 = -i+y;
if(!tpos[x1*1000+y1])
{
drawPos(x1,y1);
drawPos(x1,y2);
drawPos(x2,y1);
drawPos(x2,y2);
tpos[x1*1000+y1] = true;
}
}
document.write(html);
function drawPos(x, y)
{
html += " ";
}
} </script>
</body>
这段代码为什么什么都画不出来?
<script type="text/javascript" language="javascript">
function drawOval(x, y, a, b){
if(arguments.length == 3) {
return drawOval(x, y, a, a);
}
var i, j;
var tpos = [];
var x1, x2, y1, y2;
var html = "";
for(i = 0; i <= a; i++){
j = Math.floor(Math.sqrt(b*b - b*b*i*i/(a*a))+0.5);
x1 = i+x;
x2 = -i+x;
y1 = j+y;
y2 = -j+y;
if(!tpos[x1*1000+y1])
{
drawPos(x1,y1);
drawPos(x1,y2);
drawPos(x2,y1);
drawPos(x2,y2);
tpos[x1*1000+y1] = true;
}
}
for(i = 0; i <= b; i++)
{
j = Math.floor(Math.sqrt(a*a - a*a*i*i/(b*b))+0.5);
x1 = j+x;
x2 = -j+x;
y1 = i+y;
y2 = -i+y;
if(!tpos[x1*1000+y1])
{
drawPos(x1,y1);
drawPos(x1,y2);
drawPos(x2,y1);
drawPos(x2,y2);
tpos[x1*1000+y1] = true;
}
}
document.write(html);
function drawPos(x, y)
{
html += " ";
}
} </script>
</body>
这段代码为什么什么都画不出来?
{
html += " ";
} 用这个拼出来的html就是一串空格,拿什么画圆?