Javascript and only one Checkbox - undefined

javascript html forms checkbox

25,095

Solution 1

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...

Solution 2

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] */
}

Solution 3

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}.

Solution 4

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

Solution 5

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=""/>

View more solutions

25,095

Author by

T.T.T.

Updated on December 28, 2020

Comments

T.T.T. over 3 years

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.

jishi over 15 years

checks is the name of the <form>, user is the name of the checkbox.
chaos over 15 years

Ugh, recommending a massive framework for the simplest of tasks.
teedyay over 15 years

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! :-)
T.T.T. over 15 years

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 15 years

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