Detect focus initiated by tab key?

问题

I want to detect the focus event of an element, but only if it was initiated by the user pressing the tab key. For example:

<input type="text" id="foo" />
<input type="text" id="detect" />

If the user is focused on #foo and presses Tab, I want the event to fire once #detect becomes focused (or a conditional inside the focus event to be true). Conversely, if the user simply clicks on the #detect field to focus it, I do not want the event to fire (or I want the conditional inside the focus event call to be false).

I don't want to use the keydown event of #foo and check if the tab key was pressed, as I want the approach to be independent of any other element.

I looked through the console output of the following code, but couldn't notice any real differences between the two methods of focusing:

$('#detect').on('focus', function(e){
   console.log(e); 
});

(fiddle)

Is this possible to accomplish in a relatively simple way?

回答1:

I know you have accepted an answer but you could test the button pressed using the following:

$('#detect').on('focus', function(e){
    $(window).keyup(function (e) {
        var code = (e.keyCode ? e.keyCode : e.which);
        if (code == 9) {
           alert('I was tabbed!');
        }
    });
});

http://jsfiddle.net/LPGLm/1/

Edit: change the listener around:

$(window).keyup(function (e) {
    var code = (e.keyCode ? e.keyCode : e.which);
    if (code == 9 && $('#detect:focus').length) {
        alert('I was tabbed!');
    }
});

http://jsfiddle.net/LPGLm/7/

回答2:

A more responsive solution would be to use two listeners:

var mousedown = false;
$('#detect').on('mousedown', function () {
    mousedown = true;
});

$('#detect').on('focusin', function () {
    if(!mousedown) {
        // logic
    }
    mousedown = false;
});

Fiddle showing the difference in speed:

http://jsfiddle.net/u2y45/1/

回答3:

As you've noticed, the event object itself does not distinguish the means of access. What you can do is to bind a mousedown listener, which will fire before focus, and set some timestamp flag that you compare to some threshold value in your focus handler.

回答4:

You can check focus event on specific input by this code

$(window).on('keyup', function(event){
    if(event.keyCode == '9'){

      getFocused(event);
    }

})
var focused = 0;
function getFocused(e){
var ida =  $(':focus').eq(0).prop('id');
    if(ida=='detect' && focused==0){
        focused = 1;
        console.log(e);
    }
}

(fiddle)

回答5:

<input type="text" id="foo" />
<input type="text" id="detect" />
<script>
 $("#foo").on('keyup', function(){    
   document.getElementById("detect").value = "007";  
    alert("your tab active successfully");  
   });  
 </script>

来源：https://stackoverflow.com/questions/16144611/detect-focus-initiated-by-tab-key

标签

javascript

jquery

javascript-events

event-handling