我不懂javascript，网上找的一段打字机效果代码，离我想要的效果有点差距，麻烦各位帮忙改下，谢谢！

要求：运行后循环随机的输出typ0~typ8的内容...

<script type="text/javascript">  
var current = 0  
var x = 0  
var speed = 70  
var speed2 = 2000  
function initArray(n) {  
  this.length = n;  
  for (var i =1; i <= n; i++) {  
    this[i] = ' '  
  }  
}  
typ = new initArray(16);  
typ[0]="406:green:00000";  
typ[1]="409:green:11111";
typ[2]="384:green:22222";
typ[3]="413:green:33333";
typ[4]="371:green:44444";
typ[5]="373:green:55555";
typ[6]="379:green:66666";
typ[7]="406:green:77777";  
typ[8]="380:green:88888";  
function typewrite() {  
  var m = typ[current];  
  document.getElementById("typewriter").href = '/survey/report.html?rt=' + m.substring(0,m.indexOf(':'));  
  m = m.substring(m.indexOf(':') + 1);  
  document.getElementById("typewriter").style.color = m.substring(0,m.indexOf(':'));  
  m = m.substring(m.indexOf(':') + 1);  
  m = m.replace("&","and");  
  document.getElementById("typewriter").innerHTML = m.substring(0, x++) + "_";  
   
  if (x == m.length + 1) {  
    x = 0  
    current++  
    if (current > typ.length - 1) {  
      current = 0  
    }  
    setTimeout("typewrite()", speed2)  
    }  
  else {  
    setTimeout("typewrite()", speed)  
  }  
}  
//document.getElementById("tickertitle").innerHTML = "Latest: ";  
/*document.getElementById("smHeadlines").style.padding = "10px";*/  
typewrite()  
</script>

function getRandomFrom(firstBound, LastBound) {
        var content = 1 + LastBound - firstBound;
        return Math.floor(Math.random() * content + firstBound);
    }
document.getElementById("tickertitle").innerHTML = typ[getRandomFrom(0,8)];