浏览器底部的动态字是怎么做出来的？代码？

浏览器的状态栏里出现一个字接一个字往左跑的欢迎语！
<script language="JavaScript">
<!--
function statusMessageObject(p,d) {
this.msg = MESSAGE
this.out = " "
this.pos = POSITION
this.delay = DELAY
this.i = 0
this.reset = clearMessage
}
function clearMessage() {
this.pos = POSITION
}
var POSITION = 100
var DELAY = 5
var MESSAGE = "你要显示的文字，如：你好，博克多 "
var scroll = new statusMessageObject()
function scroller() {
for (scroll.i = 0; scroll.i < scroll.pos; scroll.i++) {
scroll.out += " "
}
if (scroll.pos >= 0)
scroll.out += scroll.msg
else scroll.out =