Javascript regex for cleaning string value

Question

I want to strip invalid characters from a string with js.

My regex currently is as below:

var newString = oldString.replace(/([^a-z0-9 ]+)/gi, '');

i.e find anything but a-z or 0-9 and spaces independent of casing and replace with nothing - however I also want to allow underscore (_), hyphen (-) and dot (.).

I attempted to update my regex as below but it is not working as expected - after I made the change I found strings with brackets () were not getting those stripped?

var newString = oldString.replace(/([^a-z0-9 .-_]+)/gi, '');

Am I missing something simple?

I always use regex 101 to test any assumptions. See the link below. I've made it multi-line for the sake of the example regex101.com/r/xY1aL3/1 — benembery
– benembery, Commented May 6, 2015 at 12:02
@benembery - thanks for the link - really useful - never came across it before — Ctrl_Alt_Defeat
– Ctrl_Alt_Defeat, Commented May 6, 2015 at 12:08

Arsenii · Accepted Answer · 2019-03-27 10:53:56Z

8

var newString = oldString.replace(/([^a-z0-9 ._-]+)/gi, '');

                                               ^^

Keep - at the end as it forms a range when placed between []. Now it is forming a range between . and _. Or you can escape it as well.

 var newString = oldString.replace(/([^a-z0-9 ._\-]+)/gi, '');

edited Mar 27, 2019 at 10:53

Arsenii

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answered May 6, 2015 at 11:41

vks

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Comments

pavel · Accepted Answer · 2015-05-06 11:44:09Z

0

You have to escape a dot and hyphen:

var newString = oldString.replace(/([^a-z0-9 \.\-_]+)/gi, '');

edited May 6, 2015 at 11:44

answered May 6, 2015 at 11:41

pavel

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3 Comments

collapsar Over a year ago

You do not have to escape a dot in character classes.

Blixt Over a year ago

Actually dots have no meaning in character ranges. The dash is the culprit.

wallop Over a year ago

within [] you dont need to escape

Tech Savant · Accepted Answer · 2015-05-06 11:47:55Z

0

Use backslash to escape . - _

this should work

.replace(/([^a-z0-9 \.\_\-]+)/gi, '');

ALSO... you can also use \w to represent letters numbers and undrescore

[a-zA-Z0-9_] == \w

edited May 6, 2015 at 11:47

answered May 6, 2015 at 11:44

Tech Savant

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6 Comments

wallop Over a year ago

within [] you dont need to escape .-_

Tech Savant Over a year ago

i think maybe you do on . and hyphen

wallop Over a year ago

hmmm a nice point made by vks below! may be using - will use it as range so you might need \ for - but not for .

Tech Savant Over a year ago

i agree with you on that one @Wishy

Tech Savant Over a year ago

Not according to popular opinion or reality even, but ok if you say so... w3schools.com/jsref/jsref_regexp_wordchar.asp

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Blixt · Accepted Answer · 2015-05-06 11:49:31Z

0

Put the literal dash last in the character class, or escape it with a backslash. Right now it's allowing an ASCII range of . to _.

var newString = oldString.replace(/[^a-z0-9 ._-]+/gi, '');

Side note: you don't need the parenthesis unless you're storing the match for something (and if parenthesis cover the whole match you don't need them then either, because \0 refers to the entire match).

edited May 6, 2015 at 11:49

answered May 6, 2015 at 11:42

Blixt

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