useOn() / useOnDocument() / useOnWindow() - Programmatic Listeners

There are times when your app needs to add a conditional listener. Sometimes a listener name is unknown, or you need to use an imperative approach to set up a listener.

Qwik provides the following functions to attach a listener:

useOn()Add an event on specific event on current host element.
useOnDocument()Add an event on specific event on document.
useOnWindow()Add an event on specific event on window.

Your task: Set up a click listener on the component to call alert('Hello world!').

Understanding the $

The $ function signals Qwik to lazy load a reference. When setting up a listener with useOn, the second argument is a Qwik URL.

Qwik URLs (QRL) are lazy-loadable references to your code. If useOn took a function directly rather than QRL, it would have to eagerly execute to allocate the listener closure. By using a QRL via the $ function, Qwik can lazy load the closure only as click listener is triggered.

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