selecting all options in a dropdown

[debugger]

I have a drop down with alot of options say about 6000 cities and
districts. I need to select all options if user selects "All checkbox".
I use "on change" and a for loop to do this, but it takes a lot of time
to select all these options. Is there any faster way to select all
these options?

function selectAll()
{
var element = document.getElementById("location");
var length = document.getElementById("location").length;

for(var i=0; i<length; i++)
{
element.options[i].selected=true;
}
}

[Lee]

debugger said:

I have a drop down with alot of options say about 6000 cities and
districts. I need to select all options if user selects "All checkbox".
I use "on change" and a for loop to do this, but it takes a lot of time
to select all these options. Is there any faster way to select all
these options?

1. 6000 entries is far too many for a drop down.
2. If you need to select all of 6000 entries, just have
a checkbox marked "all". No need to actually select them.

[debugger]

thanks for your reply. Well, i need to add few things to my question.
the total is about 6000, but this drop depends on the input from the
other drop down. So, at one time, only about five hundred are in this
drop down. Now, is there any other way of optimizing the above code?

[Paul R]

debugger wrote:

thanks for your reply. Well, i need to add few things to my question.
the total is about 6000, but this drop depends on the input from the
other drop down. So, at one time, only about five hundred are in this
drop down. Now, is there any other way of optimizing the above code?

You need to think about your architecture: a user isn't going to click
on even a fraction of 500 list entries, particularly in a dropdown,
still less in a multi-select dropdown (which are almost impossible to use).

If you have 6000 locations, then on page 1, offer "all" or
"Europe/Africa/USA, etc.". On page 2, assuming Europe, offer "all" or
"UK, France, Germany, etc.". On page 3, assuming France, offer "all" or
"Paris, Lyons, Strasbourg, etc." This isn't JavaScript, but sometimes
the best code is no code at all :-)