You can use Unpoly's
up.on
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with a named listener function and immediately unbind this event listener with { once: true }:
up.on('up:fragment:inserted', { once: true }, function () { ... })
In Unpoly 1 you can immediately unregister the listener with up.off Show archive.org snapshot :
up.on('up:fragment:inserted', function fragmentInsertedCallback() {
up.off('up:fragment:inserted', fragmentInsertedCallback)
// ... code for the callback function, which should run only once
})
Example case
I had an Unpoly compiler for a tab navigation, which sets an -active class per default to the first tab link and removes it from all other tab links. If another tab link is clicked, the -active class switches to the clicked link.
In a Jasmine spec I wanted to test this behaviour.
Unpoly's
up.hello
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emits an up:fragment:inserted event, in whose callback function I can check the default classes.
I needed to deactivate the listener to this event after it was triggered once, because it will also be triggered if I click on another tab link.
up.on('up:fragment:inserted', function fragmentInsertedCallback() {
up.off('up:fragment:inserted', fragmentInsertedCallback)
// check if tabLink1 is active, when the compiler starts
expect(tabLink1.classList.contains('-active')).toEqual(true)
expect(tabLink2.classList.contains('-active')).toEqual(false)
})
up.hello(tabNavigation) // triggers the tab navigation compiler
tabLink2.click()
expect(tabLink1.classList.contains('-active')).toEqual(false)
expect(tabLink2.classList.contains('-active')).toEqual(true)