git ssb

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module.exports = Observable
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function Observable (value, opts) {
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  var listeners = []
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  value = getValue(value, opts)
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  observable.set = function (v) {
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    value = getValue(v, opts)
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    var cachedListeners = listeners.slice(0)
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    for (var i = 0, len = cachedListeners.length; i < len; i++) {
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      cachedListeners[i](value)
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    }
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  }
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  return observable
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  function observable (listener) {
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    if (!listener) {
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      return value
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    }
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    if (typeof listener !== 'function') {
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      throw new Error('Listeners must be functions.')
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    }
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    listeners.push(listener)
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    return function remove () {
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      for (var i = 0, len = listeners.length; i < len; i++) {
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        if (listeners[i] === listener) {
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          listeners.splice(i, 1)
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          break
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        }
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      }
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    }
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  }
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}
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function getValue (value, opts) {
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  if (value == null) {
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    if (opts && opts.defaultValue != null) {
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      value = opts.defaultValue
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    } else {
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      value = null
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    }
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  }
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  return value
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}
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