| 1 | var EventEmitter = require('events').EventEmitter
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| 2 |
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| 3 | function Counter () {
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| 4 | EventEmitter.call(this)
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| 5 | this.value = 0
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| 6 | }
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| 7 |
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| 8 | Counter.prototype = Object.create(EventEmitter.prototype)
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| 9 |
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| 10 | Counter.prototype.increment = function increment () {
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| 11 | this.value++
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| 12 | }
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| 13 |
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| 14 | Counter.prototype.decrement = function decrement () {
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| 15 | if (--this.value === 0) this.emit('zero')
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| 16 | }
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| 17 |
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| 18 | Counter.prototype.isZero = function isZero () {
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| 19 | return (this.value === 0)
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| 20 | }
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| 21 |
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| 22 | Counter.prototype.onceZero = function onceZero (fn) {
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| 23 | if (this.isZero()) return fn()
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| 24 |
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| 25 | this.once('zero', fn)
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| 26 | }
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| 27 |
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| 28 | module.exports = Counter
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