On the emptying of option in object

Talking about option's emptying in <select > objects
Number of intlength as option: document.all ("Lstuserid"). Options.length;
Lstuserid for <select id=lstuserid> objects:
<select id=lstuserid>
<option >1</option>
<option >3</option>
<option >4</option>
</select>
Method One:
for (var i=0; i<intlength-1;i++)
{
document.all ("Lstuserid"). Options.remove (i);
}
Method Two:
while (document.all ("Lstuserid"). options.length>0)
{
document.all ("Lstuserid"). Option.remove (0);
}
Method one cannot empty the <select id=lstuserid> object and will make an error. Because when document.all ("Lstuserid"). Options[0] is deleted document.all ("Lstuserid"). Options[intlength-1] That is, the last option ceases to exist.
So from the last delete can be from the first deletion of the problem.
And method Two is able to empty because document.all ("Lstuserid"). Options[0] After the deletion of document.all ("Lstuserid"). Options[1] became document.all (" Lstuserid "). Options[0]. Until the last one is deleted.
#结束