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How to check checkbox checked or not using javascript ?

I have a lot of checkbox (dynamic data) . I want to know how can i check when checked chekcbox >= '1' using javascript ?

<input type="checkbox" id="1" name="test[]" onclick="test_fn()"/>
<input type="checkbox" id="2" name="test[]" onclick="test_fn()"/>
<input type="checkbox" id="3" name="test[]" onclick="test_fn()"/>
<input type="checkbox" id="4" name="test[]" onclick="test_fn()"/>

<script>
function test_fn() {
// check it's have checked checkbox or not ? //
}
</script>
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2 Answers 2

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2

Try to pass this in your inline handler,

<input type="checkbox" id="1" name="test[]" onclick="test_fn(this)"/>

And use this.checked to find out whether it is checked or not,

function test_fn(elem) {
 alert(elem.checked);
}

DEMO

To check, if the the checked check box greater than or equal to 1, then just do

function test_fn(elem) {
  if (document.querySelectorAll("input[name='test[]']:checked").length >= 1) {
    alert("yes it is greater than or equal to 1")
  }
}

DEMO

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9 Comments

@mongmongseesee Do you want something like that. See my answer.
no, i don't want to alert when checked, i want to check it's have checked checkbox >= '1' or not ?
on jsfiddle.net/9h4pek0L/3 when i uncheck for all it,s still alert yes it is greater than or equal to 1 ?
on jsfiddle.net/9h4pek0L/4 , When i checked 2 checkbox it's alert yes it is greater than or equal to 1 OK ^^ but when uncheck 1 checkbox why not alert yes it is greater than or equal to 1 ?
@mongmongseesee Sorry I misunderstood your requirement. Just check now, jsfiddle.net/9h4pek0L/5
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function test_fn()
{
    if (this.checked) return true;
    else return false;
}

Edit:

this reference won't work in this case, thanks to @RajaprabhuAravindasamy for pointing this out, read the comments or check this SO question for more information.

You need to pass a reference explicitly to the checkbox element:

function test_fn (el)
{
    if (el.checked) return true;
    else return false;
}

As for how to know if checked boxes count is more than one you can simply use a global variable to keep a track of the count like this:

var count = 0;

function test_fn (el)
{
    el.checked ? count++ : count--;
    return count > 1;
    // if (count > 1) alert ("count is more than 1");
}

Demo

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3 Comments

jsfiddle.net/9h4pek0L This will be output for this code. This inside a plain function will point the window object.
@RajaprabhuAravindasamy I was just testing it and this seems to be undefined, why is this not working?
this inside a plain function will point to window. This is not just like binding explicit event handler. So widow.checked will be evaluated to undefined.

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