Regex containg a variable

Question

Regex and variables seem to be a current issue here, yet I didn't find an answer to my problem.

It is quite simple, i am using a noSQL database system for javascript called nedb. pretty neat by the way. GitHub link

Here is the part that matters for us :

// Finding all planets whose name contain the substring 'ar' using a regular expression
db.find({ planet: /ar/ }, function (err, docs) {
  // docs contains Mars and Earth
});

as you see, the expression /ar/ means "containing the substring ar", which is classic regex. What I want is replacing ar by a variable (the result of a user search).

Like this : 
var search = ‘ar'; //taken from an HTML form
db.find ({planet : ‘/‘ + search + ‘/‘}, fonction (err,docs) {
}

This unfortunately does not work. Neither does :

  var search = ‘/ar/'; 
    db.find ({planet : search}, fonction (err,docs) {
    }

Do you have any ideas ? Might seem prettu obvious to you, but i am losing my mind on this issue aha ! thank you guys

See here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions — elclanrs, Mar 10 '14 at 09:53

score 2 · Accepted Answer · edited May 23 '17 at 11:54

2

Use the RegExp constructor :

db.find({ planet: new RegExp(yourString) }, function (err, docs) {

If your string can be anything, you'd better escape it. See this related answer then.

edited May 23 '17 at 11:54

Community

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answered Mar 10 '14 at 09:53

Denys Séguret

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hi, seems weirt but this actually works... var search = "var"; db.translation.find({translate : new RegExp(search)},function(err,docs){} yeah, without any / around... it works and thank you a lot but still.. wtf – user3401138 Mar 10 '14 at 10:02
Why does it seem weird ? – Denys Séguret Mar 10 '14 at 10:03
because the absence of / ... i'm confused but well, it works doesn't it – user3401138 Mar 10 '14 at 10:06
`/` delimits a regular expression literal, that is a regular expression that you don't have to build from a string using the RegExp contructor. – Denys Séguret Mar 10 '14 at 10:07

score 0 · Answer 2 · answered Mar 10 '14 at 09:56

0

You need to use the RegExp constructor, but this alone is not enough (. would be "any character", ? would mean the previous character is optional and / would break your regex, as well as all the other regular regex keywords and characters).

You can avoid this by using a regex escaping function (such aspreg_quote from PHPJS) which will escape them:

db.find({ planet: new RegExp(preg_quote(searchString, '/')) }, function (err, docs) {

answered Mar 10 '14 at 09:56

h2ooooooo

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hi, thank for your help, preg_quote is not recognized though.. – user3401138 Mar 10 '14 at 10:05
@user3401138: follow the link in the answer... – elclanrs Mar 10 '14 at 10:13

Regex containg a variable

2 Answers2