Awesome
ember-on-modifier
A polyfill for the {{on}}
element modifier specified by
RFC #471 "{{on}}
modifier".
Installation
ember install ember-on-modifier
Compatibility
- Completely inert when running
ember-source
3.11 or higher - Tested against
ember-source
v2.12, v2.18, v3.4 in CI
Usage
<button {{on "click" this.onClick}}>
Click me baby, one more time!
</button>
import Component from '@ember/component';
import { action } from '@ember-decorators/object';
export default class BritneySpearsComponent extends Component {
@action
onClick(event: MouseEvent) {
console.log('I must confess, I still believe.');
}
}
The @action
decorator is used to bind the onClick
method to the
component instance.
This is essentially equivalent to:
didInsertElement() {
super.didInsertElement();
const button = this.element.querySelector('button');
button.addEventListener('click', this.onClick);
}
In addition to the above {{on}}
will properly tear down the event listener,
when the element is removed from the DOM. It will also re-register the event
listener, if any of the passed parameters change.
Listening to Multiple Events
You can use the {{on}}
modifier multiple times on the same element, even for
the same event.
<button
{{on "click" this.onClick}}
{{on "click" this.anotherOnClick}}
{{on "mouseover" this.onMouseEnter}}
>
Click me baby, one more time!
</button>
Event Options
All named parameters will be passed through to
addEventListener
as the third parameter, the options hash.
<div {{on "scroll" this.onScroll passive=true}}>
Lorem Ipsum ...
</div>
This is essentially equivalent to:
didInsertElement() {
super.didInsertElement();
const div = this.element.querySelector('div');
div.addEventListener('scroll', this.onScroll, { passive: true });
}
once
To fire an event listener only once, you can pass the once
option:
<button
{{on "click" this.clickOnlyTheFirstTime once=true}}
{{on "click" this.clickEveryTime}}
>
Click me baby, one more time!
</button>
clickOnlyTheFirstTime
will only be fired the first time the button is clicked.
clickEveryTime
is fired every time the button is clicked, including the first
time.
capture
To listen for an event during the capture phase already, use the capture
option:
<div {{on "click" this.triggeredFirst capture=true}}>
<button {{on "click" this.triggeredLast}}>
Click me baby, one more time!
</button>
</div>
passive
If true
, you promise to not call event.preventDefault()
. This allows the
browser to optimize the processing of this event and not block the UI thread.
This prevent scroll jank.
If you still call event.preventDefault()
, an assertion will be raised.
<div {{on "scroll" this.trackScrollPosition passive=true}}>
Lorem ipsum...
</div>
Internet Explorer 11 Support
Internet Explorer 11 has a buggy and incomplete implementation of
addEventListener
: It does not accept an
options
parameter and sometimes even throws
a cryptic error when passing options.
This is why this addon ships a tiny ponyfill for addEventLisener
that is used internally to emulate the once
, capture
and passive
option.
This means that all currently known options
are
polyfilled, so that you can rely on them in your logic.
Currying / Partial Application
If you want to curry the function call / partially apply arguments, you can do
so using the {{fn}}
helper:
{{#each this.users as |user|}}
<button {{on "click" (fn this.deleteUser user)}}>
Delete {{user.name}}
</button>
{{/each}}
import Component from '@ember/component';
import { action } from '@ember-decorators/object';
interface User {
name: string;
}
export default class UserListComponent extends Component {
users: User[] = [{ name: 'Tom Dale' }, { name: 'Yehuda Katz' }];
@action
deleteUser(user: User, event: MouseEvent) {
event.preventDefault();
this.users.removeObject(user);
}
}
preventDefault
/ stopPropagation
/ stopImmediatePropagation
The old {{action}}
modifier used to allow easily
calling event.preventDefault()
like so:
<a href="/" {{action this.someAction preventDefault=true}}>Click me</a>
You also could easily call event.stopPropagation()
to avoid bubbling like so:
<a href="/" {{action this.someAction bubbles=false}}>Click me</a>
You can still do this using ember-event-helpers
:
<a href="/" {{on "click" (prevent-default this.someAction)}}>Click me</a>
<a href="/" {{on "click" (stop-propagation this.someAction)}}>Click me</a>
Related Projects
-
ember-on-helper
: A complimentary{{on}
template helper that accepts arbitrary event targets.{{on eventTarget eventName eventListener}}
Also ships with two convenience helpers for adding event listeners to
document
andwindow
:{{on-document eventName eventListener}} {{on-window eventName eventListener}}