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Listen to events on elements and observables.
Object<eventDescription,eventHandler(element, event)()>
An object of event names and methods that handle the event. For example:
Component.extend({
ViewModel: {
limit: "number",
offset: "number",
next: function(){
this.offset = this.offset + this.limit;
}
},
events: {
".next click": function(){
this.viewModel.next()
},
"{viewModel} limit": function(viewModel, ev, newValue){
console.log("limit is now", newValue);
}
}
});
A component’s events object is used as the prototype of a can-control. The control gets created on the component’s element.
The component’s ViewModel instance is available within event handlers as this.viewModel.
The component element is available as this.element.
Use
can-component’s events object allows you to provide low-level can-control-like abilities to a Component
while still accessing the Component’s ViewModel. The following
example listens to clicks on elements with className="next" and calls .next() on the component’s viewModel.
The events object can also listen to objects or properties on the component’s ViewModel instance. For instance, instead of using live-binding, we could listen to when offset changes and update the page manually:
Components have the ability to bind to special inserted and removed events that are called when a component’s tag has been inserted into or removed from the page:
events: {
"inserted": function(){
// called when the component’s tag is inserted into the DOM
},
"removed": function(){
// called when the component’s tag is removed from the DOM
}
}
High performance view rendering
While can-stache-bindings conveniently allows you to call a ViewModel method from a view like:
<input ($change)="doSomething()"/>
``
This has the effect of binding an event handler directly to this element. Every element that has a `on:click` or similar attribute has an event handler bound to it. For a large grid or list, this could have a performance penalty.
By contrast, events bound using can-component’s events object use event delegation, which is useful for high performance view rendering. In a large grid or list, event delegation only binds a single event handler rather than one per row.