Question 191779 in Javascript Question posted in
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Invalid regular expression error in javascript

If ‘[‘ special character is used in regex constructor object, it throws Invalid regular expression: /mat[/: Unterminated character class

function findMatch() {
   var string="Find the match";
   var text = "Mat[";

   string.replace(new RegExp(text, 'gi'),  "found")
}

Why this error is occuring and how to solve this?

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2

Answers


  1. 0

    Regular expressions use the characters [] to identify a character class– to match any character within the brackets. If you want to use either of those bracket characters as a literal, then you must escape it with a backslash. Your goal should be the regular expression:

    /Mat[/

    You’ll also need to escape the backslash itself to convert from the string to a regular expression. Thus, your code should be:

    var text = "Mat\[";
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  2. 0

    The error occurs because the square bracket character [ has a special meaning in regular expressions. It is used to define a character class, which allows specifying a set of characters that can match at that position.

    In your example, the error is occurring because the regex pattern Mat[ is not properly terminated. The closing square bracket ] is missing, causing the error message "Unterminated character class."

    To fix this issue, you need to escape the square bracket character using a backslash to treat it as a literal character instead of a special character in the regular expression.

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