JS version of the random string, suitable for the verification code OH

<!--
--------------------------Random Character--------------------------
Str_0 length
Str_1 is uppercase
str_2 whether lowercase letters
Str_3 whether the number
function Rnd_str (str_0,str_1,str_2,str_3)
{
var seed_array=new array ();
var seedary;
var i;
Seed_array[0]= ""
seed_array[1]= "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z";
Seed_array[2]= "A b c D e F g h i j k l m n o p q R S t u v w x y z";
seed_array[3]= "0 1 2 3 4 5 6 7 8 9";
if (!str_1&&!str_2&&!str_3) {str_1=true;str_2=true;str_3=true;}
if (str_1) {seed_array[0]+=seed_array[1];}
if (str_2) {seed_array[0]+= "" +seed_array[2];}
if (str_3) {seed_array[0]+= "" +seed_array[3];}
seed_array[0]= seed_array[0].split ("");
Seedary= ""
for (i=0;i<str_0;i++)
{
Seedary+=seed_array[0][math.round (Math.random () * (seed_array[0].length-1))]
}
return (seedary);
}
-->
When--------------------call--------------
<script language= "JavaScript" type= "Text/javascript" >
var obj=document.all.jz_4;
var tmp=rnd_str (6,true,true,true);
obj.value=tmp;
document.write (TMP);
</script>