How to show Javascript confirm box when checkbox is unchecked and then if user selects cancel, leave the checkbox checked?

Question

I have a small html form with three checkboxes, one in each row. I want to have a javascript confirm box show when the user unchecks the box, and then if the user selects cancel, the checkbox remains checked. I've searched this site and a few others but almost everything was to do with the checkbox being checked, like if they had to agree to some terms or something. I am very new to Javascript however I tried to make a function based on what I though it should look like, but it doesn't work.

Here is my form:

<form action="" method="post">
  <table id="table">
    <tr>
      <td>Checkbox One</td>
      <td align="center">
        <input type="checkbox" name="check1" checked="checked" onchange="cTrig(this.name)"></input>
      </td>
    </tr>
    <tr>
      <td>Checkbox Two</td>
      <td align="center">
        <input type="checkbox" name="check2" checked="checked" onchange="cTrig(this.name)"></input>
      </td>
    </tr>
    <tr>
      <td>Checkbox Three</td>
      <td align="center">
        <input type="checkbox" name="check3" checked="checked" onchange="cTrig(this.name)"></input>
      </td>
    </tr>
    <tr align="center">
      <td colspan="2">
        <input type="submit" name="submit" value="submit"></input>
      </td>
    </tr>
  </table>
</form>

And here is the function I tried, but doesn't work:

function cTrig(name) {
  if (name.checked == true) {
    confirm("Are you sure you want to do this?");
    return true;
  } else {
    return false;
  }
}

Here is a jsfiddle

I would prefer something in Javascript as I want to become more familiar with that language before getting into jquery, but if it has to be done in jquery, then that is fine. Cheers.

Answer 1

Try This Way

<form action="" method="post">
  <table id="table">
    <tr>
      <td>Checkbox One</td>
      <td align="center">
        <input type="checkbox" name ="check1" id="check1" checked='checked' onchange="cTrig('check1')"></input>
      </td>
    </tr>
    <tr>
      <td>Checkbox Two</td>
      <td align="center">
        <input type="checkbox" name="check2" id="check2" checked='checked' onchange="cTrig('check2')"></input>
      </td>
    </tr>
    <tr>
      <td>Checkbox Three</td>
      <td align="center">
        <input type="checkbox" id="check3" name="check3" checked='checked' onchange="cTrig('check3')"></input>
      </td>
    </tr>
    <tr align="center">
      <td colspan="2">
        <input type="submit" name="submit" value="submit"></input>
      </td>
    </tr>
  </table>
</form>

By Using Element Id

function cTrig(clickedid) { 
      if (document.getElementById(clickedid).checked == true) {
        return false;
      } else {
       var box= confirm("Are you sure you want to do this?");
        if (box==true)
            return true;
        else
           document.getElementById(clickedid).checked = true;

      }
    }

Working Demo

By Using Name

function cTrig(clickedid) { 
      if (document.getElementsByName(clickedid)[0].checked == true) {
        return false;
      } else {
       var box= confirm("Are you sure you want to do this?");
        if (box==true)
            return true;
        else
           document.getElementsByName(clickedid)[0].checked = true;

      }
    }

Demo Using element name

Answer 2

I would do it this way:

Your form:

<form action="" method="post">
  <table id="table">
    <tr>
      <td>Checkbox One</td>
      <td align="center">
        <input type="checkbox" name="check1" checked="checked" onchange="cTrig(this)"></input>
      </td>
    </tr>
    <tr>
      <td>Checkbox Two</td>
      <td align="center">
        <input type="checkbox" name="check2" checked="checked" onchange="cTrig(this)"></input>
      </td>
    </tr>
    <tr>
      <td>Checkbox Three</td>
      <td align="center">
        <input type="checkbox" name="check3" checked="checked" onchange="cTrig(this)"></input>
      </td>
    </tr>
    <tr align="center">
      <td colspan="2">
        <input type="submit" name="submit" value="submit"></input>
      </td>
    </tr>
  </table>
</form>

The javascript:

function cTrig(box) {
  if (!box.checked) {
    if (!confirm("Are you sure you want to do this?")) {
        box.checked = true;
    }
  }
}

Answer 3

Uses jQuery (because it's just better) but I could whip it up without if needed:

$('#check1').change(function(){
    if($("#check1").prop('checked') == false)
    {
        var i = window.confirm("Sure?");
        if(i == true)
        {
            $("#check1").prop('checked', false);
        }
        else
        {
            $("#check1").prop('checked', true);
        }
    }
});

This additionally assumes you're assigning each checkbox an id, which you will need to. Name doesn't cut it in this case.

<input type="checkbox" id="check1" name="check1" checked="checked"></input>

etc...

http://jsfiddle.net/RbENV/10/

Note that I went the native way for the confirm dialogue, but using jQuery UI you can control the box alot more.

EDIT: Added a check to make sure it only happens when you're unchecking it. Missed that part. (Note you check for false because when the change event fires the change has already happened)