admin管理员组

文章数量:1324788

In Javascript how can I tell if a checkbox has focus or not?

I thought there would be a method or property called isfocused. But apparently not.

By in focus I mean they've tabbed to it using the keyboard and at this point pressing space would check the box.

In Javascript how can I tell if a checkbox has focus or not?

I thought there would be a method or property called isfocused. But apparently not.

By in focus I mean they've tabbed to it using the keyboard and at this point pressing space would check the box.

  • javascript
  • dom
  • checkbox
Share edited Feb 11, 2009 at 0:48 Ray asked Feb 11, 2009 at 0:42 RayRay 46.6k30 gold badges127 silver badges170 bronze badges 4
  • Why do you need to know if it 'has focus'? Does that mean they've selected the label next to it? Only 'chec' and uncheck seem to matter. – George Stocker Commented Feb 11, 2009 at 0:43
  • In the javascript I'm responding to some keyboard events and I need to know if it's the last checkbox in the list. – Ray Commented Feb 11, 2009 at 0:47
  • What happens if they use a mouse? – George Stocker Commented Feb 11, 2009 at 0:49
  • Then I don't need to worry about it. It es down to if they tab past the last checkbox in the list, I need to hide the list. If they use the mouse, the list will be closed anyway. – Ray Commented Feb 11, 2009 at 0:51
Add a ment  | 

4 Answers 4

Reset to default 4

Create an event handler that is wired to the onfocus event. When it's called, set a global var to remember that it's got the focus. Write another one on the onblur event which clears the variable.

There is a onfocus event that fires when an element receives focus.

<script type="text/javascript">

var isFocused = false;

</script>

<input type="checkbox" name="team" value="team" onfocus="javascript:isFocused = true;">Spurs<br>

You might have to just hook into the onfocus and onblur events for the checkbox to keep track of when it gets and loses focus.

Here's an example of the basics of an implementation that might help you. Note: the output stuff is just for demonstration purposes and not part of the actual solution.

<html>
<head>
    <script type="text/javascript">

    onload = function()
    {
        var f = document.forms.test;
        f.focusedElem = null;
        updateOutput( f );

        for ( var i = 0, l = f.elements.length, elem; i < l; i++ )
        {
            elem = f.elements[i];
            elem.onfocus = function( elem )
            {
                return function()
                {
                    elem.form.focusedElem = elem;
                    updateOutput( elem.form );
                }
            }( elem )

            elem.onblur = function()
            {
                f.focusedElem = null;
                updateOutput( f )
            }
        }
    }

    function updateOutput( f )
    {
        document.getElementById( 'output' ).innerHTML = ( null == f.focusedElem ) ? 'Nothing!' : f.focusedElem.id;
    }

    </script>
</head>
<body>

<form name="test">

<input type="checkbox" name="foo" id="foo1">
<input type="checkbox" name="foo" id="foo2">
<input type="checkbox" name="foo" id="foo3">
<input type="checkbox" name="foo" id="foo4">

</form>

What has focus? <span id="output"></span>

</body>
</html>

本文标签： domIn Javascript find if a checkbox is focusedStack Overflow

版权声明：本文标题：dom - In Javascript find if a checkbox is focused - Stack Overflow 内容由网友自发贡献，该文观点仅代表作者本人， 转载请联系作者并注明出处：http://www.betaflare.com/web/1742141471a2422598.html， 本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌抄袭侵权/违法违规的内容，一经查实，本站将立刻删除。