58 lines
1.5 KiB
Markdown
58 lines
1.5 KiB
Markdown
# Listener
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A generator for proxy objects that run callbacks when properties are changed.
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## Interface
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```js
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listener(target={})
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// Creates a new proxy for target
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listener.listen(prop, callback)
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// Adds a callback on a property change
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listener.listen([prop, ...], callback)
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// Adds a callback to several properties at once
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listener.listen(prop)
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// Removes all callbacks from a given property
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```
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```js
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text(listener, "property")
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// Returns a text node bound to listener.property
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text(listener)
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// Returns a text node proxy for the listener
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text(listener).property
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// Same as first example
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```
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When called with two arguments, this function returns a new text node that will
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automatically update to reflect the given property on the listener.
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When called with only the listener, it creates a proxy object that, when
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indexed, returns the result of calling `text` on the listener and the indexed
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property name.
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Note that repeatedly indexing the proxy will return a new text node each time.
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## Example
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```js
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import Listener from 'listener.js'
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const listener = Listener({})
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// Listen for any changed property
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listener.listen("*", (value, prop) => console.log(`${prop} changed to ${value}`))
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// Listen only for changes to the foo property
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listener.listen("foo", prop => console.log("it was foo, by the way"))
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// Several listeners for one property are possible
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// They will be executed in order of definition
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listener.listen("foo", prop => do_something())
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listener.foo = "New Value"
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// Triggers 3 handlers
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listener.bar = "New Value"
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// Triggers only the * handler
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```
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