done purchases remove, ocr scan, read image

express-server/node_modules/multer/lib/counter.js

@@ -0,0 +1,28 @@
+var EventEmitter = require('events').EventEmitter
+
+function Counter () {
+  EventEmitter.call(this)
+  this.value = 0
+}
+
+Counter.prototype = Object.create(EventEmitter.prototype)
+
+Counter.prototype.increment = function increment () {
+  this.value++
+}
+
+Counter.prototype.decrement = function decrement () {
+  if (--this.value === 0) this.emit('zero')
+}
+
+Counter.prototype.isZero = function isZero () {
+  return (this.value === 0)
+}
+
+Counter.prototype.onceZero = function onceZero (fn) {
+  if (this.isZero()) return fn()
+
+  this.once('zero', fn)
+}
+
+module.exports = Counter