Javascript and only one Checkbox - undefined

Question

for (i = 0; i < document.checks.user.length; i++) //for all check boxes
{
    if (document.checks.user[i].checked == true )
    {
        document.checks.submit();
        return 0;
    }
}

<body>
<form action="" method=POST name="checks" ID="Form2">
  I have a bike:
  <input type="checkbox" name="user" value="Bike" ID="Checkbox1">
  <br>
  <br>
</form>
<input type="button" value="Delete" 
    class="btn" onclick="sub_delete()" 
    onmouseover="hov(this, 'btn btnhov')" onmouseout="hov(this, 'btn')" 
    id="Button1" name="Button1" 
/>
</body>

as you probably already know when there is only one check box left document.checks.user.length = undefined. Whats the most efficient way to make sure that when there is only one check box, it will be deleted. I was thinking just thinking to add it as a seperate if statement before the if statement here.....any suggesstions.

Thanks.

Why would you give all your checkboxes the same name? That doesn't make much sense. — jishi
– jishi, Commented Feb 10, 2009 at 23:15
because then you can process them as an array when it is submitted to something like php... makes perfect sense... — ftrotter
– ftrotter, Commented Aug 2, 2010 at 6:10

Josh Stodola · Accepted Answer · 2009-02-10 23:25:38Z

9

Use a loop control variable, and set it to 1 if length is undefined...

var len = document.checks.user.length;
if(len == undefined) len = 1;
for (i = 0; i < len; i++) //for all check boxes

Best regards...

answered Feb 10, 2009 at 23:25

Josh Stodola

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2 Comments

T.T.T. Over a year ago

This is what I am looking for. However, I realized when there is only one element left, the if statement I have will not work when there is only 1 element. i.e -> if (document.checks.user[0].checked == true )

T.T.T. Over a year ago

I believe it no longer sees user as an array....? I'll put the document.checks.submit(); in this loop control.

KooiInc · Accepted Answer · 2009-02-11 10:55:36Z

3

if (document.getElementById('Checkbox1').checked) { /* do something */ }

if you want to loop a bunch of checkboxes, you could loop the input fields of your form, like:

var formNodes  = document.checks.getElementsByTagName('input');
for (var i=0;i<formNodes.length;i++) {
   /* do something with the name/value/id or checked-state of formNodes[i] */
}

edited Feb 11, 2009 at 10:55

answered Feb 11, 2009 at 7:31

KooiInc

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Comments

Diodeus - James MacFarlane · Accepted Answer · 2009-02-11 05:36:32Z

1

if(document.checks.user[0]) {
  //it's an array
}
else {
  //it's a single element
}

answered Feb 11, 2009 at 5:36

Diodeus - James MacFarlane

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Comments

ftrotter · Accepted Answer · 2010-08-02 06:23:57Z

Your question is somewhat confusing, since your javascript would obviously have to be inside a function called 'sub_delete' to be any use... someone with the mighty power to edit questions might improve the question by making that clearer...

So the first issue you have to get around is the fact that for single checkbox, with a given name 'user', is not an array, and therefore has no defined length, but also if you try and access it as an array.. things get confused.. a full rewrite of your javascript function might look like this:

    function sub_delete{
        if (typeof document.checks.user.length === 'undefined') {
   /*then there is just one checkbox with the name 'user' no array*/
        if (document.checks.user.checked == true )
                            {
                                document.checks.submit();
                                return 0;
                            }   
    }else{
  /*then there is several checkboxs with the name 'user' making an array*/
        for(var i = 0, max = document.checks.user.length; i < max; i++){
            if (document.checks.user[i].checked == true )
                            {
                                document.checks.submit();
                                return 0;
                            }

        }
    }
    }//sub_delete end

HTH, -FT

amar · Accepted Answer · 2010-12-29 06:54:29Z

1

I too face the same proble with total of 5 checkboxes out of which 4 are disabled and 1 is enabled. Now the checkboxId.length is undefined, so the only option I could think of is if(checkboxId.length ==undefined ){checkboxId.checked=true & submith the form}.

answered Dec 29, 2010 at 6:54

amar

111 bronze badge

Comments

godson · Accepted Answer · 2012-12-27 10:00:19Z

1

It's very simple, just create a hidden input tag with the name same as the existing checkbox input tag.

For example:

<input type="checkbox" name="user" value="Bike" ID="Checkbox1">
<input type="hidden" name="user" value=""/>

edited Dec 27, 2012 at 10:00

answered Sep 17, 2012 at 11:39

godson

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Comments

chaos · Accepted Answer · 2009-02-10 23:19:00Z

-1

I'd probably iterate across document.checks.elements, looking for .type == 'checkbox'.

answered Feb 10, 2009 at 23:19

chaos

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Comments

teedyay · Accepted Answer · 2009-02-10 23:20:30Z

-2

jQuery is your friend:

$("input[type='checkbox']").attr('checked', false);

(... if jQuery is available to you?)

edited Feb 10, 2009 at 23:20

answered Feb 10, 2009 at 23:12

teedyay

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3 Comments

jishi Over a year ago

checks is the name of the <form>, user is the name of the checkbox.

chaos Over a year ago

Ugh, recommending a massive framework for the simplest of tasks.

teedyay Over a year ago

Heh - yeah, I take your point. I guess I'm just a bit wowed by jQuery of late: it's solved so many of my browser-specific headaches! :-)

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