CODEWITHSUNDEEP
javascriptcross-browserfocusdom-eventsblur
John Bupit
John Bupit

Reputation: 10618

Different behavior of blur event in different browsers

Consider this example where I have 2 input fields:

<input id="a" />
<input id="b" style="display: none" />

And consider the following JavaScript, which is an attempt to do this:

Show #b only when #a has focus and hide #b whenever #a loses focus, except when #a loses its focus to #b.

$("#a").focus(function() {
    $("#b").show();
});

$("#a, #b").blur(function() {
    $("#b").hide();
});

$("#b").focus(function(){
    $("#b").show();
});


$("#a").focus(function() {
  $("#b").show();
});

$("#a, #b").blur(function() {
  $("#b").hide();
});

$("#b").focus(function() {
  $("#b").show();
});
#b {
  display: none;
}
<input id="a" value=a>
<input id="b" value=b>
<br/>^ focus on the input

The above code is incorrect as $("#b").focus() would never be triggered because as soon as #a loses focus, #b is hidden. This expected behavior is observed in Firefox (Version 24.6.0).

But in Chrome (Version 35.0), the code seems to run incorrectly (or correctly!?).

Clearly, the b.focus event is still being registered in Chrome. Why does this event register in Chrome, but not in Firefox?

Update

As pointed out by raina77ow:

Here's a fiddle without using jQuery, producing the same behavior.

Upvotes: 12

Views: 9828

Answers (3)

John Bupit
John Bupit

Reputation: 10618

According to this archive of whatwg.org:

An element is focusable if the user agent's default behavior allows it to be focusable or if the element is specially focusable, but only if the element is either being rendered or is a descendant of a canvas element that represents embedded content.

It seems that all browsers also don't make visibility:hidden and display:none input elements focusable. The following JavaScript tests in which cases is an element focusable.

function isFocusable(type) {
    var element = document.getElementById(type);
    result += type + ' is';
    try {
        element.focus();
        if (element != document.activeElement)
            result += ' not';
    } catch (e) {
      result += ' not (error thrown)';
    }
    result += ' focusable<br>';
}


var result = '';

function isFocusable(type) {
  var element = document.getElementById(type);
  result += type + ' is';
  try {
    element.focus();
    if (element != document.activeElement)
      result += ' not';
  } catch (e) {
    result += ' not (error thrown)';
  }
  result += ' focusable<br>';
}

isFocusable('text');
isFocusable('hidden');
isFocusable('disabled');
isFocusable('readonly');
isFocusable('visiblity-hidden');
isFocusable('display-none');
isFocusable('div-hidden');

document.getElementById('browser-version').innerHTML = navigator.userAgent;
document.getElementById('logger').innerHTML += result;
<input id=text type=""></input>
<input id=hidden type="hidden"></input>
<input id=disabled disabled></input>
<input id=readonly readonly></input>
<input id=visiblity-hidden style="visibility:hidden"></input>
<input id=display-none style="display:none"></input>
<div id=div-hidden sytle="visibility:hidden" tabindex=1>
  </input>

  <div id=browser-version></div>

  <div id=logger></div>

Here's the output in Firefox 34.0.5 and Chrome 39.0.2

Gecko/20100101 Firefox/34.0
text is focusable
hidden is not focusable
disabled is not focusable
readonly is focusable
visiblity-hidden is not focusable
display-none is not focusable
div-hidden is focusable

AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.95 Safari/537.36
text is focusable
hidden is not focusable
disabled is not focusable
readonly is focusable
visiblity-hidden is not focusable
display-none is not focusable
div-hidden is focusable

Upvotes: 0

Indranil Mondal
Indranil Mondal

Reputation: 2857

You can use an extravarible to check whether b is focused before hiding b. It worked in IE, Chrome & Firefox. I don;t have any other browser. You can check it. 

var focusedB = false;
$("#a").focus(function(){
     $("#b").show();   
 });
 //if b is focused by pressing tab bar.
 $("#a").keydown(function(e){
     if(e.which === 9){
          focusedB = true;  
      }
   });
   $("#b").blur(function(){
        $("#b").hide();
   });
   $("#a").blur(function(){
       if(focusedB){
            focusedB = false;
        }else{
            $("#b").hide();
        }
    });
    $( "#b" ).mousedown(function() {
       focusedB = true;
    });

Upvotes: 4

Nateowami
Nateowami

Reputation: 1036

As you know, the issue is that different browsers choose to call event handlers in different orders. One solution is to give the other events a chance to fire by setting a timer for 0 milliseconds, and then checking the fields to see which (if any) is focused.

a.onfocus = function() {show(b);};

a.onblur = function() {
    setTimeout(function() {
        //if neither filed is focused
        if(document.activeElement !== b && document.activeElement !== a){
            hide(b);
        }
            }, 0);
};

//same action as for a
b.onblur = a.onblur;

Tested in Chrome, Firefox, Internet Explorer, and Safari. See full working example (edited version of your fiddle) at JSFiddle.net.

Upvotes: 9

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