Listboxes and Arrays(Cot'd)...

interrupt · #1 (**permalink**) August 3rd, 2004, 10:09 AM

Ok,

If I select a choice with 5 elements in its array (these 5 elements populate a new listbox by dynamically assigning each array element as a new option) then I select a new choice with for example 3 elements in its array, I still have two of the old elements in the 2nd listbox! How do I dynamically remove unnecessary choices from a list box?

This is my script so far, but I get an infinite loop:

function nullify(){
while(document.form1.select1.options.length > 1){
null1()
}
function null1(){
document.form2.select2.options[1] = null;
}
}
</script>
Thanks In Advance
interrupt

ChrisScott · #2 (**permalink**) August 3rd, 2004, 10:43 AM

Hi Interrupt,

Give this a try...

Code:

<script type="text/javascript">
// array of options
var listBox2Options =    [    
                            [],
                            ["option 1", "1", "option 2", "2", "option 3", "3", "option 4", "4", "option 5", "5"],
                            ["option 1", "1", "option 2", "2", "option 3", "3", "option 4", "4", "option 5", "5", "option 6", "6", "option 7", "7"]    
                        ];

function LoadListBox2(pListBox1){
    var listBox2 = document.getElementById("ListBox2");
    while(listBox2.options.length > 0){
        listBox2.remove(0);
    }
    var options = listBox2Options[pListBox1.selectedIndex];
    for(var i = 0; i < options.length; i += 2){
        listBox2.options.add(new Option(options[i], options[i + 1]));
    }
}
</script>

...

<form id="myForm" name="myForm">
    <select id="ListBox1" name="ListBox1" onchange="LoadListBox2(this);">
        <option value="0">(choose)</option>
        <option value="1">one</option>
        <option value="2">two</option>
    </select>

    <select id="ListBox2" name="ListBox2"></select>
</form>

Best regards,

Chris

Randhy · #3 (**permalink**) August 10th, 2004, 11:03 PM

You declare a value of document.form1.select1.options.length > 1, this will make your statement loop if the value of the object you have declared is larger than 1. Of course you get an infinite loop, cause you have have more than 1 options. You should add a break; statement if a condition is fullfiled. With break you can stop your loop and go to the next line of statement.

Cheers, too.

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