# Yahoo! UI Library

### event 3.0.0b1

Yahoo! UI Library > event > focusblur.js (source view)
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    (function() {

    var adapt = Y.Env.evt.plugins,
        CAPTURE_CONFIG = { capture: true },
        NOOP  = function(){},

        // Opera implents capture phase events per spec rather than
        // the more useful way it is implemented in other browsers:
        // The event doesn't fire on a target unless there is a
        // listener on an element in the target's ancestry.  If a
        // capture phase listener is added only to the element that
        // will be the target of the event, the listener won't fire.
        // To get around this, we register a NOOP listener on the
        // element's parent.
        _captureHack = function(type, o) {
            var el = (Y.Lang.isString(o)) ? Y.Selector.query(o, null, true) : o,
                p  = el && el.parentNode;

            if (p) {
                Y.Event._attach([type, NOOP, p], CAPTURE_CONFIG);
            }
        };

    /**
     * Adds a DOM focus listener.  Uses the focusin event in IE,
     * and the capture phase otherwise so that
     * the event propagates in a way that enables event delegation.
     *
     * Note: if you are registering this event on the intended target
     * rather than an ancestor, the element must be in the DOM in
     * order for it to work in Opera.
     *
     * @for YUI
     * @event focus
     */
    adapt.focus = {
        on: function(type, fn, o) {
            var a = Y.Array(arguments, 0, true);
            if (Y.UA.opera) {
                _captureHack(type, o);
            }
            return Y.Event._attach(a, CAPTURE_CONFIG);
        }
    };

    /**
     * Adds a DOM blur listener.  Uses the focusout event in IE,
     * and the capture phase otherwise so that
     * the event propagates in a way that enables event delegation.
     *
     * Note: if you are registering this event on the intended target
     * rather than an ancestor, the element must be in the DOM
     * at the time of registration in order for it to work in Opera.
     *
     * @for YUI
     * @event blur
     */
    adapt.blur = {
        on: function(type, fn, o) {
            var a = Y.Array(arguments, 0, true);
            if (Y.UA.opera) {
                _captureHack(type, o);
            }
            return Y.Event._attach(a, CAPTURE_CONFIG);
        }

    };

    })();

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