# qooxdoo

## the new era of web development

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# Problems with “this” in event handlers

How do I ensure that the correct “this” is referred to in an event handler? Say you have an event-handler within a custom widget which looks like this:

    _someHandler : function(e) {
        alert(this);
    }

and then later within the same class definition, register a handler with another class instance:

    var anotherWidget = new AnotherWidget();
    anotherWidget.addEventListener("changeSomething", this._someHandler);

When the handler gets triggered by a “changeSomething” event, the alert of the handler is being called. However, there is a problem in that ‘this’ now refers to an object of class AnotherWidget and not to the instance of MyWidget. To solve this problem, use:

    anotherWidget.addEventListener("changeSomething", this._handler, this);