MongoDB RegEx not working

问题

I'm trying to return documents that whose obsNum field starts with 1.. I have written the following RegEx to filter out those documents however, it returns all the documents that start with 1

Observations.getObservationsModelObject().find({
    "ageGroup": ageGroup,
    "obsNum": {
        $regex: '^\s*1\.'
    }
}, function(err, foundData) {});

What am I doing wrong?

This RegEx '^\s*1\.' is returning the following instead of returning on 1.3, 1.1 & 1.2:

obsNum:  1.3
obsNum:  1.1
obsNum:  1.2
obsNum:  123
obsNum:  121`

回答1:

'^\s*1\.' is a string. The regex after removing backshash escaping will be ^s*1. which means, the string should start with any number of space/s followed by 1 and then any character.

You can use regex literal syntax

$regex: /^\s*1\./

or double-escape backslashes

$regex: '^\\s*1\\.'

I recommend to use literal syntax whenever possible as it is easy and less error-prone.

回答2:

The regular expression you might try is:

^(1\.\d+)

Explanation:

• ^ Beginning of the string
• (…) Capturing parentheses: remember the match
• 1 Literal digit
• \d decimal digit
• + At least one

来源：https://stackoverflow.com/questions/43449823/mongodb-regex-not-working