Introduction to regjsparser

regjsparser is a powerful JavaScript library for parsing regular expressions. It allows developers to understand and manipulate the abstract syntax tree (AST) of regular expressions effortlessly.

Why Use regjsparser?

Understanding the structure of regular expressions can be challenging. With regjsparser, you can parse, traverse, and manipulate the AST of regex patterns, which provides greater control and insight into their structure.

Key APIs

parse

Parses a regular expression string into its AST representation.

  
    const regjsparser = require('regjsparser');
    const ast = regjsparser.parse("/\\d+/");
    console.log(JSON.stringify(ast, null, 2));
  

traverse

Traverse the AST with a visitor pattern.

  
    function traverse(node, callback) {
      callback(node);
      if (node.body) {
        node.body.forEach(child => traverse(child, callback));
      }
    }
    
    traverse(ast, node => {
      console.log(node.type);
    });
  

generate

Generate a regular expression string from an AST.

  
    const regexString = regjsparser.generate(ast);
    console.log(regexString); // Output: /\d+/
  

Example App Using regjsparser

Let’s create a simple Node.js application that uses regjsparser to parse and manipulate regular expressions.

  
    const regjsparser = require('regjsparser');

    function highlightPattern(regex, string) {
      const ast = regjsparser.parse(regex.toString());
      let highlighted = '';
      traverse(ast, node => {
        if (node.type === 'Literal') {
          highlighted += `${node.raw}`;
        } else {
          highlighted += node.raw;
        }
      });
      return highlighted;
    }

    const pattern = /hello \w+/;
    const text = 'hello world';
    const result = highlightPattern(pattern, text);
    console.log(result);
  

The above example demonstrates how to use regjsparser to traverse and manipulate a regex AST, highlighting matched patterns within a string.

Hash: 1b609258600751b6f2260c0bf2428aa19834a99e7be0111eb660b7b79bf3c4c0