Question

I am using mongodb to build an app which get the user's twitter timeline in a mongodb database, I want to check if the tweets I got from twitter has already existed in my database, so I use the mongodb.find() function.

The whole function is like this:

db.collection.find({'twitterIAlreadyStored.id_str': newTweet.id_str}

Then I want to write a logical code which is:

if(exist){
} else {

}

So I am wondering if there is any way to test if the result of find exists or not??

Answer 1

db.collection.find仅在您使用mongo shell时才有效。你所追求的是mongoose次查询，因为你标记了mongoose我会假设你已经设置了它。

假设您的model名称为twitterIAlreadyStored

以及property

中的id_str

您要查找的value是newTweet.id_str

这将是以下格式：

var mongoose = require('mongoose');

mongoose.model('MODELNAME').findOne({'PROPERTY': 'VALUE'}, function(error, exist) {
  if(exist && !error){
    //do something
  } else {
    //IF YOU ARE USING EXPRESS.JS, YOU MUST USE RES.SEND() or RES.END() TO TERMINATE THE CONNECTION
    res.status(500).send({"message" : "Not Found"});
    return;
  }
};

res.send（）和res.end（）

上的

express.js doc

How to test if a value exists?

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