When a ‘blur’ event occurs, how can I find out which element focus went *to*?

When a ‘blur’ event occurs, how can I find out which element focus went *to*?

Suppose I attach an blur function to an HTML input box like this:

Is there a way to get the ID of the element which caused the blur event to fire (the element which was clicked) inside the function? How?
For example, suppose I have a span like this:
Hello World

If I click the span right after the input element has focus, the input element will lose its focus. How does the function know that it was mySpan that was clicked?
PS: If the onclick event of the span would occur before the onblur event of the input element my problem would be solved, because I could set some status value indicating a specific element had been clicked.
PPS: The background of this problem is that I want to trigger an AJAX autocompleter control externally (from a clickable element) to show its suggestions, without the suggestions disappearing immediately because of the blur event on the input element. So I want to check in the blur function if one specific element has been clicked, and if so, ignore the blur event.

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Solutions/Answers:

Solution 1:

Hmm… In Firefox, you can use explicitOriginalTarget to pull the element that was clicked on. I expected toElement to do the same for IE, but it does not appear to work… However, you can pull the newly-focused element from the document:

function showBlur(ev)
{
   var target = ev.explicitOriginalTarget||document.activeElement;
   document.getElementById("focused").value = 
      target ? target.id||target.tagName||target : '';
}

...

<button id="btn1" onblur="showBlur(event)">Button 1</button>
<button id="btn2" onblur="showBlur(event)">Button 2</button>
<button id="btn3" onblur="showBlur(event)">Button 3</button>
<input id="focused" type="text" disabled="disabled" />

Caveat: This technique does not work for focus changes caused by tabbing through fields with the keyboard, and does not work at all in Chrome or Safari. The big problem with using activeElement (except in IE) is that it is not consistently updated until after the blur event has been processed, and may have no valid value at all during processing! This can be mitigated with a variation on the technique Michiel ended up using:

function showBlur(ev)
{
  // Use timeout to delay examination of activeElement until after blur/focus 
  // events have been processed.
  setTimeout(function()
  {
    var target = document.activeElement;
    document.getElementById("focused").value = 
      target ? target.id||target.tagName||target : '';
  }, 1);
}

This should work in most modern browsers (tested in Chrome, IE, and Firefox), with the caveat that Chrome does not set focus on buttons that are clicked (vs. tabbed to).

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Solution 2:

2015 answer: according to UI Events, you can use the relatedTarget property of the event:

Used to identify a secondary EventTarget related to a Focus
event, depending on the type of event.

For blur events,

relatedTarget: event target receiving focus.

Example:

function blurListener(event) {
  event.target.className = 'blurred';
  if(event.relatedTarget)
    event.relatedTarget.className = 'focused';
}
[].forEach.call(document.querySelectorAll('input'), function(el) {
  el.addEventListener('blur', blurListener, false);
});
.blurred { background: orange }
.focused { background: lime }
<p>Blurred elements will become orange.</p>
<p>Focused elements should become lime.</p>
<input /><input /><input />

Note Firefox won’t support relatedTarget until version 48 (bug 962251, MDN).

Solution 3:

I solved it eventually with a timeout on the onblur event (thanks to the advice of a friend who is not StackOverflow):

<input id="myInput" onblur="setTimeout(function() {alert(clickSrc);},200);"></input>
<span onclick="clickSrc='mySpan';" id="mySpan">Hello World</span>

Works both in FF and IE.

Solution 4:

It’s possible to use mousedown event of document instead of blur:

$(document).mousedown(function(){
  if ($(event.target).attr("id") == "mySpan") {
    // some process
  }
});

Solution 5:

The type FocusEvent instances have relatedTarget attribute, however, up to version 47 of the FF, specifically, this attribute returns null, from 48 already works.

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You can to see more here.

Solution 6:

I am also trying to make Autocompleter ignore blurring if a specific element clicked and have a working solution, but for only Firefox due to explicitOriginalTarget

Autocompleter.Base.prototype.onBlur = Autocompleter.Base.prototype.onBlur.wrap( 
        function(origfunc, ev) {
            if ($(this.options.ignoreBlurEventElement)) {
                var newTargetElement = (ev.explicitOriginalTarget.nodeType == 3 ? ev.explicitOriginalTarget.parentNode : ev.explicitOriginalTarget);
                if (!newTargetElement.descendantOf($(this.options.ignoreBlurEventElement))) {
                    return origfunc(ev);
                }
            }
        }
    );

This code wraps default onBlur method of Autocompleter and checks if ignoreBlurEventElement parameters is set. if it is set, it checks everytime to see if clicked element is ignoreBlurEventElement or not. If it is, Autocompleter does not cal onBlur, else it calls onBlur. The only problem with this is that it only works in Firefox because explicitOriginalTarget property is Mozilla specific . Now I am trying to find a different way than using explicitOriginalTarget. The solution you have mentioned requires you to add onclick behaviour manually to the element. If I can’t manage to solve explicitOriginalTarget issue, I guess I will follow your solution.