String pattern to regex

Question

I'm using mongodb to store data. I would like to store complete regular expressions as strings:

{
  permissions: [{
    resName: '/user[1-5]/ig',
    isRegex: true
  }]
}

I know there is the module mongoose-regexp which can store RegExp, but I would like to store regex and strings in the same field.

I've achieved it using eval(user.permissions[i].resName).test(resName). I would like to know if this is the correct approach and if there is any alternative (i.e. using new RegExp(...))

EDIT

I'm trying to avoid eval as this field is comming from user input and it could be a problem if something malitious is sent to db.

You could use new RegExp but you'd need to remove the delimiters (/) and separate the flags (ig) — Phil
– Phil, Commented Mar 8, 2017 at 23:02

Phil · Accepted Answer · 2017-03-08 23:49:13Z

2

This should get you there

const rxFinder = /^\/(.+)\/((g|i|m|u|y)*)$/
const resName = '/user[1-5]/ig'

const resRx = new RegExp(...rxFinder.exec(resName).slice(1))

console.info(resRx)

const testStrings = ['String for User5, eh', 'Bad User7 string']

testStrings.forEach(str => {
  console.info(JSON.stringify(str), 'is a match:', resRx.test(str))
})

edited Mar 8, 2017 at 23:49

answered Mar 8, 2017 at 23:09

Phil

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7 Comments

Scott Sauyet Over a year ago

This version will fail if there are no flags. You might want to make those optional.

Miquel Over a year ago

const matches = /^\/(.+)\/([a-z]*)$/g.exec(resName); maybe could work, then new RegExp(matches[0], matches[1]);, this way the flags will also be conserved

Phil Over a year ago

@Miquel not sure what you mean there

Miquel Over a year ago

@Phil I see that there are also Uppercase moddifiers, so maybe the good solution for rxFinder would be /^\/(.+)\/([a-zA-Z]*)$/g. Regarding speed, if I understand well is it better to use new RegExp(matches[0], matches[1]);?

Phil Over a year ago

@Miquel according to the docs for JavaScript's RegExp, the flags are limited to gimuy

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