# did-upsert Modifier that is called when a DOM node is inserted and/or an argument is updated. Additionally the callback function provided should expect an event shaped object rather than a reference to a DOM node itself, therefore the DOM node can be obtained by referencing `target` or `currentTarget` instead. This means that you can use the same callback function for both `{{on 'click'}}` modifiers and `{{did-upsert}}` modifiers. The one dowbside is that the signature of functions used for `did-upsert` are slightly different than when you use `did-insert/did-update`, but moving forwards we are more likely to make `did-insert/did-update` use a more standard based signature (or some other approach to make things consistent) ```hbs <div {{did-upsert this.callback @arrayThatMightGetAddedToTODetectAnUpdate.length}} > </div> ``` ```javascript callback(e) { console.log(e.currentTarget); console.log(e.target); } ``` Other than the above exception, the modifer works the same as the `did-insert/did-update` modifiers.