55 lines
1.4 KiB
JavaScript
55 lines
1.4 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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const registry = new Map()
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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) => prop=="listen"
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? listen
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: target[prop]
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})
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registry.set(proxy, target)
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return proxy
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}
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listener.raw = proxy => registry.get(proxy)
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export const text = (listener, prop) => {
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if (prop) {
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const node = document.createTextNode(listener[prop])
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listener.listen(prop, data => node.data = data)
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return node
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} else {
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return new Proxy(listener, {
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get: (target, prop, receiver) => text(listener, prop)
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})
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}
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}
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export default listener
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