Angular error nothing to repeat on valid regex

Question

I use the following regex: /https{1}:\/\/(?:\$INSTANCE\$)(?:\/\w+){0,255}(?:\?\w+=\w+){0,1}(?:\&\w+=\w+){0,255}/ysg and the following url-like structure for a match: https://$INSTANCE$/eng/route?param=val&parameter3=value&prmtr=value event though the regex is valid, Angular keeps giving this error: SyntaxError: nothing to repeat

I validated the regex using this site: https://regex101.com/r/6x4kP2/1

Anyone know what is wrong with the regex?

The code where I use it:

patternCustomTSConfigURL = "https{1}:\/\/(?:\$INSTANCE\$)(?:\/\w+){0,255}(?:\?\w+=\w+){0,1}(?:\&\w+=\w+){0,255}",
    this.exampleForm = new FormGroup({
       url: new FormControl(this.url, [
          Validators.required,
          Validators.minLength(5),
          Validators.maxLength(255),
          Validators.pattern(patternCustomTSConfigURL)
        ])
    });

It might be better if you could give us some more context, show the code where you actually use this regex. — Andy Preston, May 08 '23 at 08:50

score 1 · Answer 1 · answered May 08 '23 at 08:21

You have to be careful with escaping characters in JavaScript. When copy pasting regex from internet, special characters usually aren't escaped, so you have to modify it manually.

Check the following: What does the "Nothing to repeat" error mean when using a regex in javascript?

Ravikumar · Accepted Answer · 2023-05-08T10:08:46.260

Like @chuftica already mentioned you have to be very careful escaping characters.

As per mdn below two are same

const re = /\w+/;
// OR
const re = new RegExp("\\w+");

So, you have to use your regEx like below when it's a string format

patternCustomTSConfigURL = "https{1}:\\/\\/(?:\\$INSTANCE\\$)(?:\\/\\w+){0,255}(?:\\?\\w+=\\w+){0,1}(?:\\&\\w+=\\w+){0,255}",

OR like below when it's RegExp instance

patternCustomTSConfigURL = /https:\/\/(?:[$]INSTANCE[$])(?:\/\w+){0,255}(?:\?\w+=\w+){0,1}(?:\&\w+=\w+){0,255}/,

P.S. it's nothing to do with Angular, as Angular just concatenate start of the string ^ and end of the string $ matchers to the string if you don't specify it explicitly

Angular code Ref: https://github.com/angular/angular/blob/80fe08be96633171567e30eb91dd1d23c60a2952/packages/forms/src/validators.ts#L533

Thanks alot, it was because of the bad escaping of special chars. — rhea, May 08 '23 at 10:32

Angular error nothing to repeat on valid regex

2 Answers2