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Posted by Michael Winter on 12/16/05 20:44
On 16/12/2005 18:27, Ed Jay wrote:
[snip]
> function get_menu_value(menu_name) {
>
> var mValue = 0;
>
> for(var i=0; i < menu_name.length; i++) {
Why does the length of the name determine the number of iterations of
this loop?
> if (document.form1.elements[menu_name+(i)].checked) {
The expression in the square brackets will be evaluated, converted to a
string, and used as a property name. In your example, these names will
be 'choice0', 'choice1', ..., 'choice5'. Not only are there only five
checkboxes (you create six names), none of these names match a control
within the form, resulting in an undefined value, and an error with the
subsequent property access.
> mValue = mValue + document.form1.elements[menu_name+(i)].value;
The value property is a string. The addition operator, with a string and
a number operand, will perform a concatenation. I suspect that you want
arithmetic addition.
[snip]
> return false;
[snip]
> <input type = "submit" onclick="get_menu_value('choice')">
As you do not return the value returned by the get_menu_value function,
it will have no effect. In any case, it is generally better to use the
submit event of the form, passing a reference to the form, rather than
the click event of the button.
function getMenuValue(menuName, form) {
var value = 0,
menu = form.elements[menuName];
for(var i = 0, n = menu.length; i < n; ++i) {
if(menu[i].checked) {
/* Unary plus performs explicit conversion to Number. */
value += +menu[i].value;
}
}
alert(value);
return false;
}
<form action="..." onsubmit="return getMenuValue('choice', this);">
<!-- ... -->
</form>
Hope that helps,
Mike
--
Michael Winter
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