61 lines
1.5 KiB
JavaScript
61 lines
1.5 KiB
JavaScript
/*
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A somewhat refined Proxy generator that lets you selectively listen to changed
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properties and react accordingly.
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Example:
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const l = listener()
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l.listen("contract", contract => speaker.handle(contract))
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l.contract = new Contract()
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*/
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export const listener = (target={}) => {
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let callbacks = new Map()
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function listen(prop, callback) {
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if ("object" == typeof prop && "forEach" in prop) {
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prop.forEach(prop => this.listen(prop, callback))
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} else if (callback) {
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let list = callbacks.get(prop)
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if (!list) callbacks.set(prop, list=[])
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list.push(callback)
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} else {
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callbacks.delete(prop)
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}
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}
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let proxy = new Proxy(target, {
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set: (target, prop, value) => {
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if (callbacks.has("*")) callbacks.get("*").forEach(callback => callback(value, prop, target[prop]))
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if (callbacks.has(prop)) callbacks.get(prop).forEach(callback => callback(value, prop, target[prop]))
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return Reflect.set(target, prop, value)
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},
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get: (target, prop, value) => {
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if (prop == "listen")
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return listen
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else if (prop == "__raw")
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return target
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else
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return Reflect.get(target, prop)
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}
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})
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return proxy
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}
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export const bindContent = (listener, prop="value", target=document.createTextNode(""), filter) => {
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const run = data => {
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data = filter
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? filter(data)
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: data
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if ("innerText" in target)
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if (typeof data == "string")
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target.innerText = data
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else
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target.replaceChildren(data)
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else
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target.data = data
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}
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listener.listen(prop, run)
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run(listener[prop])
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return target
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}
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export default listener
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