Regex involving curly braces not working, while for square brackets it does

Question

I have this regex that matches something like [abc] as a string pattern, with the help of
"[]": "((\\[[^\\]]*($|\\]))(\\][^\\]]*($|\\]))*)

So it will catch [ABC] from ABC AB [ABC] BC . So anything enclosed in a square bracket.

It works as it's supposed to.

Then I wrote an expression like
"{{}}": "((\\{\\{[^\\}\\}]*($|\\}\\}))(\\}\\}[^\\}\\}]*($|\\}\\}))*)"

to catch something like {{abc}} . Now, this does work in online regex testers, it catches {{abc}} from ABC AB {{ABC}} BC .

But it's not doing anything when I have it in a JS code. While, the square bracket expression does what it's supposed to. Am I missing something?

  createStringRegex(stringTypes) {
    return new RegExp('^(' + this.createStringPattern(stringTypes) + ')', 'u');
  }

  // This enables the following string patterns:
  // 1. backtick quoted string using `` to escape
  // 2. square bracket quoted string (SQL Server) using ]] to escape
  // 3. double quoted string using "" or \" to escape


  createStringPattern(stringTypes) {
    const patterns = {
      '``': '((`[^`]*($|`))+)',
      '[]': '((\\[[^\\]]*($|\\]))(\\][^\\]]*($|\\]))*)',
      "{{}}": "((\\{\\{[^\\}\\}]*($|\\}\\}))(\\}\\}[^\\}\\}]*($|\\}\\}))*)",
      '""': '(("[^"\\\\]*(?:\\\\.[^"\\\\]*)*("|$))+)',
      "''": "(('[^'\\\\]*(?:\\\\.[^'\\\\]*)*('|$))+)",
      "N''": "((N'[^N'\\\\]*(?:\\\\.[^N'\\\\]*)*('|$))+)"
    };

    return stringTypes.map(t => patterns[t]).join('|');
  }

This is the whole snippet surrounding this

Answer 1

I don't see the problem. I also tried to use your code and it seems to work:

 function createStringRegex(stringTypes) { return new RegExp('^(' + this.createStringPattern(stringTypes) + ')', 'u'); } // This enables the following string patterns: // 1. backtick quoted string using `` to escape // 2. square bracket quoted string (SQL Server) using ]] to escape // 3. double quoted string using "" or \" to escape function createStringPattern(stringTypes) { const patterns = { '``': '((`[^`]*($|`))+)', '[]': '((\\[[^\\]]*($|\\]))(\\][^\\]]*($|\\]))*)', "{{}}": "((\\{\\{[^\\}\\}]*($|\\}\\}))(\\}\\}[^\\}\\}]*($|\\}\\}))*)", '""': '(("[^"\\\\]*(?:\\\\.[^"\\\\]*)*("|$))+)', "''": "(('[^'\\\\]*(?:\\\\.[^'\\\\]*)*('|$))+)", "N''": "((N'[^N'\\\\]*(?:\\\\.[^N'\\\\]*)*('|$))+)" }; return stringTypes.map(t => patterns[t]).join('|'); } console.log("[abc]".match(createStringRegex(["[]"]))); // it matches console.log("{{abc}}".match(createStringRegex(["{{}}"]))); // it matches console.log("[abc]".match(createStringRegex(["{{}}"]))); // it doesn't match