Develop Reference

REGEX working in chrome but breaks in safari

The following javascript regex breaks in safari getting SyntaxError: Invalid regular expression: invalid group specifier name"
/^(?!\s)[A-Za-z0-9\'\.\-\,\s]*(?<!\s)$/.test('ABCD##');
Can someone please help me to re write the regex which can work in safari?
I find out that safari doesn't support lookbehind but still not able to re write the whole regex which can be good for safari.

Modify your pattern to avoid the negative lookbehind. Since you seem to want a non whitespace character as the last character, just use a character class for that.
/^(?!\s)[A-Za-z0-9'.,\s-]*[A-Za-z0-9'.,-]$/.test('ABCD##')
Side note: your current pattern looks wrong for what you are trying to match.

Regex - unhandled js exception in react native

I am using the following regex in my react-native app.
This is an email validation regex :
^[\w]+#((?:[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?\.)+)(?:[A-Za-z0-9-]{2,63}(?<!-))
This works fine in the browser but crashes the react native app due to the following :
no stack', reason: 'Unhandled JS Exception: Invalid regular expression: invalid group specifier name
Could someone please help getting this to work on react native, maybe by achieving the same thing that this regex achieves but without the lookbehind expression ?

The problem is likely caused the by the (?<!-) negative lookahead at the end of the regex pattern, which your JavaScript engine does not support. To ensure that a hyphen does not occur at the end of the email, we can simply use:
^[\w]+#((?:[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?\.)+)(?:[A-Za-z0-9-]{1,62}[A-Za-z0-9])
That is, just use [A-Za-z0-9] to represent the final of 63 possible characters in the pattern.

This regex will not work likely problem in regex pattern i think.
this works for me for simple email format abc#mail.com
var regex = /^(([^<>()\[\]\\.,;:\s#"]+(\.[^<>()\[\]\\.,;:\s#"]+)*)|(".+"))#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;

React app working on Chrome & Firefox but not on Safari and every IOS browser [duplicate]

In my Javascript code, this regex /(?<=\/)([^#]+)(?=#*)/ works fine in Chrome, but in safari, I get:
Invalid regular expression: invalid group specifier name
Any ideas?

Looks like Safari doesn't support lookbehind yet (that is, your (?<=\/)). One alternative would be to put the / that comes before in a non-captured group, and then extract only the first group (the content after the / and before the #).
/(?:\/)([^#]+)(?=#*)/
Also, (?=#*) is odd - you probably want to lookahead for something (such as # or the end of the string), rather than a * quantifier (zero or more occurrences of #). It might be better to use something like
/(?:\/)([^#]+)(?=#|$)/
or just omit the lookahead entirely (because the ([^#]+) is greedy), depending on your circumstances.

Just wanted to put this out there for anyone who stumbles across this issue and can't find anything...
I had the same issue, and it turned out to be a RegEx expression in one of my dependencies, namely Discord.js .
Luckily I no longer needed that package but if you do, consider putting an issue out there or something (maybe you shouldn't even be running discord.js in your frontend react app).

The support for RegExp look behind assertions as been issued by web kit:
Check link: https://github.com/WebKit/WebKit/pull/7109

Regex ?<= not supported Safari iOS, we can use ?:
Note: / or 1st reference letter that comes before in a non-captured group
See detail: https://caniuse.com/js-regexp-lookbehind
let str = "Get from Slash/to Next hashtag #GMK"
let workFineOnChromeOnly = str?.match(/(?<=\/)([^#]+)(?=#*)/g)
console.log("❌ Work Fine On Chrome Only", workFineOnChromeOnly )
let workFineSafariToo = str?.match(/(?:\/)([^#]+)(?=#*)/g)
console.log("✔️ Work Fine Safari too", workFineSafariToo )

How to setup Eclipse to be warned about trailing comma in JavaScript

As many of us know, IE7 is not quite friendly with JavaScript code containing trailing commas, which can be a large problem for projects using modern JS framerworks and containing a lot of JS code.
In a pretty good article on the subject, the author mentions:
On the tools front, my preference for combating these devils is the Eclipse JavaScript Development Tools. The JavaScript source editor in JSDT flags trailing commas as errors: http://www.enterprisedojo.com/wp-content/uploads/2010/12/jsdtRules.png
However, using Eclipse Indigo with WTP/JSDT, I'm not seeing trailing commas as errors, and I can't find a proper setting to fix this.
How do I setup Eclipse to flag trailing commas in JavaScript as errors?

It looks like the fix for another bug involving erroneous syntax errors on the comma operator also removed the syntax error on trailing commas in initializers. That's technically correct; the standard says they're allowed and IE7 is just nonconformant. There's a feature request open asking that they be reinstated.

Slightly off topic, but you should also look into using JSLint to check the syntax of the JavaScript code. It will warn you about the trailing comma, but also about many other potential problems. There is a good plugin for Eclipse, http://marketplace.eclipse.org/content/phonegap-android-jslintjshint. The instructions for setting it up: http://www.mobiledevelopersolutions.com/home/announce-1/mds12released-nowwithjslintjshint

Make sure you're in the correct perspective (ie JavaScript as opposed to Java).
Also, I found in Helios that if I added a JS file to the project by right-clicking and adding a new 'File' (which I would then name with a .js extension) didn't make the UI pick up that it should be treated as a JS file--no syntax highlighting, checking, etc. If I added it specifically using the new JavaScript file option, it worked fine.

help making a "universal" regex Javascript compatible

I found a very nice URL regex matcher on this site: http://daringfireball.net/2010/07/improved_regex_for_matching_urls . It states that it's free to use and that it's cross language compatible (including Javascript). First of all, I have to escape some of the slashes to get it to compile at all. When I do that, it works fine on Rubular.com (where I generally test regexes), with the strange side effect that each match has 5 fields: 1 is the url, and the extra 4 are empty. When I put this in JS, I get the error "Invalid Group". I am using Node.js if that makes any difference, but I wish I could understand that error. I'd like to cut back on the unnecessary empty match fields, but I don't even know where to begin diagnosing this beast. This is what I had after escaping:
(?xi)\b((?:[a-z][\w-]+:(?:\/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}\/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’] ))

Actually, you don't need the first capturing group either; it's the same as the whole match in this case, and that can always be accessed via $&. You can change all the capturing groups to non-capturing by adding ?: after the opening parens:
/\b(?:(?:[a-z][\w-]+:(?:\/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}\/)(?:[^\s()<>]+|\((?:[^\s()<>]+|(\(?:[^\s()<>]+\)))*\))+(?:\((?:[^\s()<>]+|(?:\(?:[^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’]))/i
That "invalid group" error is due to the inline modifiers (i.e., (?xi)) which, as #kirilloid observed, are not supported in JavaScript. Jon Gruber (the regex's author) was mistaken about that, as he was about JS supporting free-spacing mode.
Just FYI, the reason you had to escape the slashes is because you were using regex-literal notation, the most common form of which uses the forward-slash as the regex delimiter. In other words, it's the language (Ruby or JavaScript) that requires you to escape that particular character, not the regex. Some languages let you choose different regex delimiters, while others don't support regex literals at all.
But these are all language issues, not regex issues; the regex itself appears to work as advertised.

Seemes, that you copied it wrong.
http://www.regular-expressions.info/javascript.html
No mode modifiers to set matching options within the regular expression.
No regular expression comments
I.e. (?xi) at the beginning is useless.
x is useless at all for compacted RegExp
i can be replaced with flag
All these result in:
/\b((?:[a-z][\w-]+:(?:\/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}\/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’]))/i
Tested and working in Google Chrome => should work in Node.js