CODEWITHSUNDEEP
javascriptregexsafari
user3253067
user3253067

Reputation: 113

Regex created with constructor not working with Safari

It is documented that one can create regex expressions using 2 methods:

1.simple expression

   /ab+c/i;

2.using a constructor

  new RegExp(/ab+c/, 'i');
  new RegExp('ab+c', 'i');

I have used the version RegExp(/ab+c/, 'i') which passed in Chrome, Mozilla but not in Safari, returning an error:

cannot supply flags when constructing one regexp from another

I have switched to the first method and it works now but there are 2 things that are not clear for me:

  1. what does '/' character stand for in an expression like that. I've seen it added by default in online regex test sites

  2. why safari failed to work with the version that i used

Upvotes: 1

Views: 4969

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626747

The regex constructor notation (new RegExp(...)) is mainly used when you need to pass a variable to your pattern. If the pattern is "hard-coded", use a regex literal straight away: var reg = /ab+c/i. See more on when to use which notation here.

Safari currently does not accept a regex literal as the first argument to the RegExp constructor, nor do some other browsers. Thus, it is safer to pass a regular string pattern as the first argument.

As for the /.../, these are regex delimiters that delimit action/pattern/modifiers. In JS, the action part is not used, and the modifiers are limited to i (case-insensitive), g (global matching) and m (multiline mode to redefine the ^ and $ behavior so that they could match the start/end of a line instead of the start/end of a string).

Upvotes: 1

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