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.
8 answers
solution1
8 ACCPTED 2009-02-10 23:25:38
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...
solution2
3 2009-02-11 07:31:27
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] */
}
solution3
1 2012-09-17 11:39:18
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=""/>
solution4
1 2010-08-02 06:23:57
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
solution5
1 2010-12-29 06:54:29
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}.
solution6
1 2009-02-11 05:36:32
if(document.checks.user[0]) {
//it's an array
}
else {
//it's a single element
}
solution7
-1 2009-02-10 23:12:22
jQuery is your friend:
$("input[type='checkbox']").attr('checked', false);
(... if jQuery is available to you?)
solution8
-1 2009-02-10 23:19:00
我可能会遍历document.checks.elements，寻找.type =='checkbox'。
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