Issue with RegExp escape function - Javascript

Question

Trying to escape special characters. I type $ or ^ or | it works fine. Why is my below code not escaping () {} ? * + and \ when I type these I get invalid expression error.

escape = function(value) {
    return value.replace(/[\-\[\]{}()*+?.,\\\^$|#\s]/g, "\\$&");
}

something wrong with the above expression???

MDN suggests this

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

even this I'm facing the same issue. no error for {} $ ^ | but I get error for () * ? \ +

They don't need to be escaped because they are inside a [ ] (which means they are part of a character class), if the were outside they would need to be escaped to be matched as normal characters. — Nelson Benítez León
– Nelson Benítez León, Commented May 8, 2020 at 2:19
So if I have to escape [ ] or ? or * I need to put them outside [ ]. Because when I type () or ? or + or * or \ I get the invalid regular exp error. I do not get that error for {} $ # | ^ — grooot
– grooot, Commented May 8, 2020 at 2:41

Jack Bashford · Accepted Answer · 2020-05-08 02:30:21Z

1

They're in a character class (denoted by []) meaning that they don't need to be escaped. They only need to be escaped when they're outside of a character class and in the regex, as they would denote certain operations (like {1,3} meaning "One to three times inclusive").

Also a small point of clarification for your question - the code's not escaping \, you're escaping \ by putting two of them together - \\ is the escape for \. So only {} and () are not being escaped, to answer the question at the top of your post.

answered May 8, 2020 at 2:30

Jack Bashford

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1 Comment

grooot Over a year ago

ok I'm really confused Jack!!! When I type {} or $ or # or ^ or | no error is being thrown. But when I type () or ? or + or * or \ I get the invalid regular exp error. How did my function escape $ {} and all but not ? + \

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