29 lines
570 B
JavaScript
29 lines
570 B
JavaScript
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var EventEmitter = require('events').EventEmitter
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function Counter () {
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EventEmitter.call(this)
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this.value = 0
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}
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Counter.prototype = Object.create(EventEmitter.prototype)
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Counter.prototype.increment = function increment () {
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this.value++
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}
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Counter.prototype.decrement = function decrement () {
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if (--this.value === 0) this.emit('zero')
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}
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Counter.prototype.isZero = function isZero () {
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return (this.value === 0)
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}
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Counter.prototype.onceZero = function onceZero (fn) {
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if (this.isZero()) return fn()
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this.once('zero', fn)
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}
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module.exports = Counter
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