how do I check if at least one of several checkboxes has been checked?

[NotGiven]

I have a form with several questions. Within each question there are
several checkboxes. I need to ensure that the user checks at least one
checkbox. They can check more but must check at least one.

How would I do this in Javascript?

Many thanks.

 

[Erwin Moller]

I have a form with several questions. Within each question there are
several checkboxes. I need to ensure that the user checks at least one
checkbox. They can check more but must check at least one.

How would I do this in Javascript?

Many thanks.

Yes, it is easy.

Name your checkboxes in your HTML.
You can check if checkbox myCheck in form myForm is checked like this:

var isChecked = document.forms.myForm.myCheck.checked;

the .checked returns true or false or errors when the object you used it on
doesn't have checked-property.

if (isChecked) {
// checked is true
alert ("checkbox myCheck is checked.");
}


Regards,
Erwin Moller

 

[Fabian]

NotGiven hu kiteb:

I have a form with several questions. Within each question there are
several checkboxes. I need to ensure that the user checks at least
one checkbox. They can check more but must check at least one.

How would I do this in Javascript?

Define a global variable. Increment/decrement it by 1 each time a
checkbox is checked/unchecked. When submitting, check to see that the
variable is >0.

 

[Richard Cornford]

"Erwin Moller"
message

var isChecked = document.forms.myForm.myCheck.checked;

the .checked returns true or false or errors when the object you
used it on doesn't have checked-property.

If the object referenced exists but has no - checked - property that
assignment should assign undefined rather than erroring. It would
produce
an error if myCheck, myForm, the forms collection and/or document did
not exist (refer to objects(/functions)).

if (isChecked) {
// checked is true
alert ("checkbox myCheck is checked.");
}

In the absence of a - checked - property, and the - isChecked - variable
having been assigned undefined the - if - statement would type-convert
undefined to boolean, yielding false.

Richard.

 

[NotGiven]

Great idea - thanks

NotGiven hu kiteb:


Define a global variable. Increment/decrement it by 1 each time a
checkbox is checked/unchecked. When submitting, check to see that the
variable is >0.


--

 

[Thomas 'PointedEars' Lahn]

NotGiven hu kiteb:

Define a global variable.

Evil[tm]. I would prefer to use a property of the parent "form" element
object which allows to be referred as "this.form.property" in the
"onclick" event handler of the respective "input[type='checkbox']" element.


PointedEars