How to use regex in mongodb query?

@denis 

To use regular expressions in a MongoDB query, you can use the $regex operator in the query document.

Here is an example of how to use the $regex operator in a MongoDB query:

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db.collection.find({ field: { $regex: /pattern/ } })

This will find all documents in the collection where the value of the field field matches the regular expression pattern.

You can also use the $options operator to specify options for the regular expression, such as case insensitivity. For example:

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db.collection.find({ field: { $regex: /pattern/i } })

This will find all documents in the collection where the value of the field field matches the regular expression pattern, ignoring case.

You can also use the $regex operator in other MongoDB operators, such as $match in the pipeline of an aggregate function.

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db.collection.aggregate([
   {
      $match: {
         field: { $regex: /pattern/ }
      }
   }
])

This will find all documents in the collection where the value of the field field matches the regular expression pattern and return them as part of the aggregation pipeline.