Using Regex on Express with MongoDB

Question

I want to use regex to find records that match certain pattern on Express.js using MongoDB.

Here is my code

var urlList = [];
var db = req.db;
var collection = db.get('project');

var regex = '/^'+url+'/';
console.log('regex = '+regex);
collection.find({url: { $regex: regex, $options: 'i' }},function(err,list){

    console.log('length = '+list.length);
    var arrayUrl = [];
    for (var i=0;i<list.length;i++){
        console.log(list[i].url);
        arrayUrl.push(list[i].url);
    }
});

But I got list.length = 0 although the database contains the records that match the pattern for sure.

Using the following command on cmd

db.project.find({url:{$regex:/^Projek-1/,$options: 'i'}});

I got the results I want.

How to use regex on express.js to find matched records in MongoDB database?

you are passing string instead of regex object. Try using new RegExp — hassansin
– hassansin, Commented Jul 10, 2015 at 14:35
You are using URL string as a regex? You will most likely have to escape it: var regex = new RegExp("^"+url.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&'), 'i');, and remove the , $options: 'i' from the later code. Please check. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 10, 2015 at 14:40
I am not sure you see that, but ^ makes the regex match at the beginning of the string only. You will need to remove it if you want to match multiple occurrences of a pattern. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 10, 2015 at 14:48

cmlndz · Accepted Answer · 2015-07-10 14:39:47Z

2

First, you don't really need to use $regex, you'll do fine with url: /foobar/i.

Anyway, the problem is that you are not creating a proper RegExp object, only a string that looks like one. Use a proper one by creating a new instance of RegExp

Example:

var re = new RegExp("^" + url);

...

find({url: re})

answered Jul 10, 2015 at 14:39

cmlndz

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