node.js 如何在 mongodb-native findOne() 中使用变量作为字段名？
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How to use a variable as a field name in mongodb-native findOne()?
提问by WillMcavoy
I have this data in mongodb:
我在 mongodb 中有这些数据：
{
"name": "Amey",
"country": "India",
"region": "Dhule,Maharashtra"
}
and I want to retrieve the data while passing a field name as a variable in query.
我想在将字段名称作为查询中的变量传递时检索数据。
Following does not work:
以下不起作用：
var name = req.params.name;
var value = req.params.value;
collection.findOne({name: value}, function(err, item) {
res.send(item);
});
How can I query mongodb keeping both field name and its value dynamic?
如何查询 mongodb 保持字段名称及其值动态？
回答by maxdec
You need to set the key of the query object dynamically:
您需要动态设置查询对象的键：
var name = req.params.name;
var value = req.params.value;
var query = {};
query[name] = value;
collection.findOne(query, function (err, item) { ... });
When you do {name: value}, the key is the string 'name'and not the value of the variable name.
当你这样做时{name: value}，关键是字符串'name'而不是变量的值name。
回答by KiwenLau
Just put the variable in []
只需将变量放入 []
var name=req.params.name;
var value = req.params.value;
collection.findOne({[name]:value}, function(err, item) {
res.send(item);
});
回答by hydrix
I'd like to clarify that if you're trying to make a query concerning a nested field only (not its value), like if you want to query the field "name" from this document:
我想澄清一下，如果您试图仅对嵌套字段（而不是其值）进行查询，例如您想从本文档中查询字段“名称”：
{
loc: [0, 3],
unit: {
name : "playername"
}
}
this will work (as in my case - using update):
这将起作用（在我的情况下 - 使用更新）：
mdb.cords.updateOne(
{_id: ObjectID(someid)},
{$set: {[query]: newValue}},
function (err, result) {
...
}
}
Simply enclosing [query]in brackets tells mongodb that it's not literal, but rather a path.
简单地[query]用括号括起来告诉 mongodb 它不是文字，而是一条路径。
