<head>
<script>
/*** A ball bouncing in a textarea box by Neil Robertson , 16/11/96 ***/
bstr=" \n"+
" \n"+
" \n"+
" \n"+
" \n"+
" \n"+
" \n"+
" \n"+
" \n"+
" \n";
ballx=3;
bally=0;
addx=1;
addy=1;
pos=3;
pos2=pos;
speed=100;
/*** Insert char into string ***/
function insert_char(str,ch,pos)
{
var tmp1=str.substring(0,pos);
var tmp2=str.substring(pos+1,str.length);
str=tmp1+ch+tmp2;
return str;
}
/*** Bounce the ball ***/
function bounce()
{
bstr=insert_char(bstr,"O",pos);
document.form.text.value=bstr;
ballx+=addx;
bally+=addy;
if (ballx==19 || ballx==0) addx=-addx;
if (bally==9 || bally==0) addy=-addy;
pos=ballx+bally*20+bally;
bstr=insert_char(bstr," ",pos2);
pos2=pos;
setTimeout("bounce()",speed);
}
</script>
</head>
<body onLoad="bounce()">
<font color=blue><h1>A Bouncing Ball</h1></font>
This is a simple little routine written in JavaScript<br>
to bounce a ball around a textarea box. <br>
<form name="form">
<textarea name="text" cols=20 rows=10></textarea><br>
<font color=green><input type=button value="<< Slower" onClick="speed+=5;">
<font color=red><input type=button value="Faster >>" onClick="speed-=5; if (speed<0) speed=0;">
</form>
</body>