Beginner Exercism • javascript

Grep

Challenge Overview

Search files for lines matching a search string and return all matching lines.

💡 View Solution

export const grep = (pattern, flags, files) => {
  const showLineNumber = flags.includes('-n');
  const onlyFileNames = flags.includes('-l');
  const caseInsensitive = flags.includes('-i');
  const invertMatch = flags.includes('-v');
  const matchEntireLine = flags.includes('-x');

  const multipleFiles = files.length > 1;
  let results = [];

  for (const file of files) {
    const lines = readFileSync(file, 'utf8').split('\n');
    let fileMatched = false;

    for (let i = 0; i < lines.length; i++) {
      const line = lines[i];
      let isMatch = false;

      const p = caseInsensitive ? pattern.toLowerCase() : pattern;
      const l = caseInsensitive ? line.toLowerCase() : line;

      if (matchEntireLine) {
        isMatch = (p === l);
      } else {
        isMatch = l.includes(p);
      }

      if (invertMatch) isMatch = !isMatch;

      if (isMatch) {
        fileMatched = true;
        if (onlyFileNames) break;

        let output = '';
        if (multipleFiles) output += `${file}:`;
        if (showLineNumber) output += `${i + 1}:`;
        output += line;
        results.push(output);
      }
    }

    if (onlyFileNames && fileMatched) {
      results.push(file);
    }
  }

  return results.join('\n');
};