Javascript/Angular: Where to put small helper functions

Question

I'm working on an angular app, which I kind of inherited. I saw that there was a bug with unescaped regex so I wanted to add a function for escaping regex like so:

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}

No big deal, right? But where to put this? The regex is used inside a controller. But does it make sense to have this escapeRegExp function inside the scope like so:

                    $scope.escapeRegExp = function(string) {
                      return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
                    }

I'm a little confused where best to put these little functions. What's the best practice?

You only put things in the $scope if the ui needs to have access to it. If it does, then that's a perfectly fine place to put it. — Dimitrios Matanis
– Dimitrios Matanis, Commented Jan 5, 2021 at 11:20

Drag13 · Accepted Answer · 2021-01-05 11:18:08Z

2

If you expect to reuse this piece of code - put it to the separate module (utils/common/shared) as a service

If you expect to use this piece of code only for this controller - extract it to the separate file as a function

answered Jan 5, 2021 at 11:18

Drag13

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4 Comments

Toto Over a year ago

I expect to use this piece of code only inside the controller. Can I just throw the first version (without $scope) inside the controller definition and call it a day, or is it better to define the function somewhere else?

Drag13 Over a year ago

From my experience, if you are dealing with regex (or math operations) it's much better to keep them separate and heavily cover with tests. Regexes are really fragile and subject to change. This approach will save you from bugs when requirements will change.

Toto Over a year ago

I agree with you about keeping things separate, but it's a huge project and I just want to fix this one bug where regex is not escaped properly before executing a match. Therefore I want to add this one-liner in order to escape a string. From that the question arose where to put such tiny one-liners in angularjs/javascript. So it is fine, to just have a non-scope helper-function inside the controller definition, I assume?

Drag13 Over a year ago

I would say it's OK

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