Registers a function that is when a matching element is inserted into the DOM.
This code registers a function that is called when an element with a .foo
class
enters the DOM:
up.compiler('.foo', function(element, data, meta) {
// do something with `element`
})
The compiler function is passed three arguments:
element
matching the selectorWhen a compiler registers effects outside the compiling element's subtree, it must return a destructor function that reverts the effect. The destructor function is called automatically when the element is swapped or destroyed later.
Examples for non-local effects are global event handlers bound to
the document
, or setInterval()
:
up.compiler('.current-time', function(element) {
let update = () => element.textContent = new Date().toString()
let updateInterval = setInterval(update, 1000)
return () => clearInterval(updateInterval)
})
See cleaning up after yourself for more details and examples.
When multiple elements in update match the selector, the compiler function is called once for each element.
Let's say a fragment with three .card
elements is inserted and compiled:
<div class="fragment">
<div class="card">...</div>
<div class="card">...</div>
<div class="card">...</div>
</div>
A compiler function for .card
would be called three separate times:
up.compiler('.card', function(card, data) {
// chip: called three times
})
If you would like the compiler to run once for all matches within
a render pass, use a { batch: true }
option:
up.compiler('.card', { batch: true }, function(cards, datas) {
console.debug(`We have ${cards.length} new cards`)
})
It is safe to throw exceptions from a compiler or its destructor. A crashing compiler will not interrupt a render pass, or prevent other compilers on the same element.
Exceptions thrown by compiler functions are logged to the browser's error console.
Unpoly also emits an error
event on window
.
See errors in user code for details.
Compilers are called in the order they were registered.
You can control the order by passing a { priority }
option.
The default priority is 0
. Compilers with a higher priority are run first.
up.compiler('.foo', { priority: 999 }, function() {
// called before compilers with a lower priority
})
When a compiler sets an Unpoly attribute, this usually has no effect, since attributes have already been evaluated. Use a macro instead.
See Rendering lifecycle for a full overview of Unpoly's rendering steps.
Compiler functions can be async
.
This is useful when a compiler needs to fetch network
resources, or when calling a library with an asynchronous API:
up.compiler('textarea.wysiwyg', async function(textarea) { // mark: async
let editor = await import('wysiwyg-editor') // mark: await
editor.init(textarea) // mark: await
})
You can also use this to split up expensive tasks, giving the browser a chance to render and process user input:
up.compiler('.element', async function(element) {
doRenderBlockingWork(element)
await scheduler.yield() // mark-line
doUserVisibleWork(element)
})
Like synchronous compilers, async compiler functions can return a destructor function:
up.compiler('textarea.wysiwyg', async function(textarea) {
let editor = await import('wysiwyg-editor')
editor.init(textarea) // mark: await
return () => editor.destroy(textarea) // mark-line
})
Unpoly guarantees that the destructor is called, even if the element gets destroyed before the compiler function terminates.
Unpoly will run the first task of every compiler function before allowing the browser to render DOM changes. If an async compiler function runs for multiple tasks, the browser will render between tasks. If you have render-blocking mutations that should be hidden from the user, these must happen in the first task.
Async compilers will not delay the promise returned by rendering functions up.render()
or up.layer.open()
.
Async compilers will delay the promise returned by up.render().finished
and up.hello()
.
When you deliver your JavaScript in multiple files, you may register compilers after Unpoly was booted.
When compilers are registered after Unpoly was booted, it is run on current elements, but only if the compiler has the default priority.
If the compiler has a non-default priority, it is run on future
fragments only. In this case either remove the { priority }
option
or manually call up.hello()
on an element that should be
recompiled.
The selector to match.
The priority of this compiler.
Compilers with a higher priority are run first. Two compilers with the same priority are run in the order they were registered.
If set to true
and a fragment insertion contains multiple
elements matching selector
, the compiler
function is only called once
with all these elements.
The function to call when an element matching selector
is inserted.
Up to three arguments can be accepted:
element
matching the selectorThe function may return a destructor function that is called before it is removed from the DOM. The destructor function is called with the compiled element.
The compiler function can be async
.