title: How to update multiple documents in mongoose
body: <p>My schema:<pre>
  fruits: {
  type: string,
  },
  days: {
  type: Number
  }</pre>
  I have an Array of fruit sold today
  a=[apple,mango,guava,banana]</p>
  <p>Documents:</p>
  <pre>
   {  
     _id:12381823281
     fruits:mango,
      days: 3
  }
  {  
     _id:12381823282
     fruits:apple,
      days: 5
  }
  </pre>
  <p>now  I have to check in db whether doc.fruit== a[i] for each element of a and if exist  increment day number by one and if not create new document with
  {
  fruit=a[i],
  ,days:1
  }
  i.e</p>
  <p>I want to get
  Updated Document as</p>
  <pre>
   {  
     _id:12381823281
     fruits:mango,
      days: 4
  },
  {  
     _id:12381823282
     fruits:apple,
      days: 6
  },
  {  
     _id:12381823283
     fruits:banana,
      days: 1
  },
  {  
     _id:12381823284
     fruits:guava,
      days: 1
  }
  </pre>
  <p>How to do it without using forloop</p>