阅读中文版本

Regex Tester CLI

A Node CLI that tests a regular expression against input text or stdin, printing every match with its index and capture groups.

node --version

node regex.mjs "\w+@\w+" "a@b c@d"

node --test regex.test.mjs

Prints each match with its character index and any capture groups, or reports no matches.

What it does

Compiles the pattern with the global flag and iterates matches, guarding against zero-length matches that would otherwise loop forever. Each match reports its index, span, and capture groups.

const [pattern, ...rest] = process.argv.slice(2);
const text = rest.join(' ') || '';
if (!pattern) { console.error('usage: regex <pattern> <text>'); process.exit(1); }

let re;
try { re = new RegExp(pattern, 'g'); } catch (e) { console.error('invalid regex: ' + e.message); process.exit(1); }

let m; let count = 0;
while ((m = re.exec(text)) !== null) {
  const start = m.index; const end = start + m[0].length;
  console.log('match ' + start + '..' + end + ': ' + m[0] + (m.length > 1 ? ' groups=[' + m.slice(1).join(',') + ']' : ''));
  count++;
  if (m.index === re.lastIndex) re.lastIndex++;
}
if (count === 0) console.log('no matches');

Run and verify

node regex.mjs "\w+@\w+" "a@b c@d"

Run the test command to check the implementation: node --test regex.test.mjs.

Expected Output

Matching an email-like pattern against a@b c@d yields two matches on one line each:

match 0..3: a@b
match 4..7: c@d

Limitations

Uses JavaScript regex semantics, which lack some features other engines have and include catastrophic-backtracking pitfalls; a pathological pattern from stdin can stall the process.