js/listener.md
DarkWiiPlayer f612273632 Rename bind to bindContent in listener.js
This is partly to avoid confusion with the skooma `bind` function,
but also to make it clearer that only the inner content of an element is
being bound to the listener.

This function may also disappear entirely in the future if it turns out
it doesn't provide any benefits over the skooma bind function.
2021-11-25 10:08:52 +01:00

54 lines
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Markdown

# Listener
A generator for proxy objects that run callbacks when properties are changed.
## Interface
```js
listener(target={})
// Creates a new proxy for target
listener.listen(prop, callback)
// Adds a callback on a property change
listener.listen([prop, ...], callback)
// Adds a callback to several properties at once
listener.listen(prop)
// Removes all callbacks from a given property
```
```js
bindContent(listener, "value")
// Returns a text node with listener.value as its content
// that will change whenever the value is changed
bindContent(listener, "value", html_element)
// Binds an existng HTML or Text node
bindContent(listener, "value", html_element, value => value.toUpperCase())
// Accepts a function to transform the value
bindContent(listener, "value", html_element, value => document.createElement("hr"))
// Also accepts HTML elements when the target is not a text node
```
This function *may* be **removed** in the future if it doesn't show any
usefullnes that isn't already provided by the skooma bind function.
## Example
```js
import Listener from 'listener.js'
const listener = Listener({})
// Listen for any changed property
listener.listen("*", (value, prop) => console.log(`${prop} changed to ${value}`))
// Listen only for changes to the foo property
listener.listen("foo", prop => console.log("it was foo, by the way"))
// Several listeners for one property are possible
// They will be executed in order of definition
listener.listen("foo", prop => do_something())
listener.foo = "New Value"
// Triggers 3 handlers
listener.bar = "New Value"
// Triggers only the * handler
```