Unable to check if a javascript checkbox array element is checked or not?

Question

What is want is - when the checkbox is checked option no. 5 in select list will be selected and when the checkbox is unchecked option no. 0 will be selected in the select list.

The select list and the checkboxes are generated dynamically in the php code as below :

echo "<select name='coupons".$i."' id='coupons".$i."'>";
------- All Options --------
echo "</select>";


<input type='checkbox' name='myCheckbox[]' value='<?php echo $i."_".$row->id; ?>' onclick='setCCode("myCheckbox[]",<?php echo $i;?>)'> 

 -----------------------------------------------------------------------------

Solved the second requirement on my own now ..... thanks to all for your inputs

just added the following line in the checkAll() within the for loop

setCCode(children[i],i+1);

The javascript function :

function setCCode(checkbox_name,i) 
{   
    var form_object = document.getElementsByName(checkbox_name+"["+i+"]");
    var selname = document.getElementsByName("coupons"+i)[0];

    if(form_object.checked) {
            selname.selectedIndex = 5;
    }
    else {
        selname.selectedIndex = 0;
    } 
}

The above issue is solved....... thanks to all

Now what i need to do is when a user checks a checkbox to select or deselect all the dynamically generated checkboxes on the form the above logic should work.

<input type='checkbox' name='checkall' onChange="checkAll(this, 'myCheckbox[]')">
<span class="chkall">Check / Uncheck All</span>

<input type='checkbox' name='myCheckbox[]' value='<?php echo $i."_".$row->id; ?>' onclick='setCCode(this,<?php echo $i;?>)'>

The javascript code i am using to select/deselect all checkboxes on form is as below :

function checkAll(parent, field)
{
    var children = document.getElementsByName(field);
    var newValue = parent.checked;

    for (i = 0; i < children.length; i++){
    if (children[i].disabled == false) {    
        children[i].checked = newValue;
    }
    }
}

function setCCode(Sender,i) 
{   
  document.getElementsByName("coupons"+i)[0].selectedIndex = Sender.checked ? 5 : 0;
}

Mircea Soaica · Accepted Answer · 2011-09-23 06:23:07Z

2

getElementsByName returns an array of objects. Replace the line with:

var form_object = document.getElementsByName(checkbox_name+"["+i+"]")[0];

answered Sep 23, 2011 at 6:23

Mircea Soaica

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1 Comment

Sandy505 Over a year ago

getting the error message as below when i am doing what u suggested Error: form_object is undefined Source File: localhost:82/rajib/admin/free_members_ajax.php Line: 71

Jan Pfeifer · Accepted Answer · 2011-09-23 06:32:38Z

0

You can pass refference to the checkbox itself as a parameter

<input type='checkbox' name='myCheckbox[]' value='<?php echo $i."_".$row->id; ?>' onclick='setCCode(this,<?php echo $i;?>)'>

function setCCode(Sender,i) 
{   
  document.getElementsByName("coupons"+i)[0].selectedIndex = Sender.checked ? 5 : 0;
}

answered Sep 23, 2011 at 6:32

Jan Pfeifer

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Comments

RobG · Accepted Answer · 2011-09-23 06:41:37Z

0

If you have a reference to the form that the checkbox is in, and it has a unique name in the form, then you can access it as:

form_object = form.elements[ checkbox_name + "[" + i + "]" ];

and you can also use the ternary operator to make the code more concise:

selname.selectedIndex = form_object.checked? 5 : 0;

Edit

Sorry, missed the obvious. If you pass a refereference to the checkbox in the handler, then you can also get the form (all form controls have a form property that references the form they are in). So as Jan Pfeifer suggested (abbreviated markup):

<input ... onclick='setCCode(this, <?php echo $i;?>)'>

then the script is just:

function setCCode(checkbox, i) 
{   
    checkbox.form.elements['coupons' + i].selectedIndex = checkbox.checked? 5 : 0;
}

edited Sep 23, 2011 at 6:41

answered Sep 23, 2011 at 6:28

RobG

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2 Comments

Sandy505 Over a year ago

Error: form_object is undefined Source File: localhost:82/rajib/admin/free_members_ajax.php Line: 72 function setCCode(checkbox_name,i) { var form_object = document.forms[0].elements[ checkbox_name + "[" + i + "]" ]; var selname = document.getElementsByName("coupons"+i)[0]; selname.selectedIndex = form_object.checked? 5 : 0; }

RobG Over a year ago

Did you assign a reference to the form to the variable form first as specified?

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