Fydler UtilityBelt - Regex Tester

Regex Tester

Text & Development Tool

Pattern

Flags

Test String

Matches

No matches.

Highlighted Matches

Common Regex Patterns

\d+ — digits
[a-zA-Z]+ — letters
^\s+|\s+$ — leading/trailing whitespace
[\w.-]+@[\w.-]+\.\w+ — basic email
https?://[\w./-]+ — basic URL
(?<=@)\w+ — lookbehind (characters after @)

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lucide.createIcons(); const patternInput = document.getElementById('regex-pattern'); const flagsInput = document.getElementById('regex-flags'); const testInput = document.getElementById('regex-input'); const matchesOutput = document.getElementById('regex-matches'); const errorOutput = document.getElementById('regex-error'); function testRegex() { const pattern = patternInput.value; const flags = flagsInput.value; const text = testInput.value; errorOutput.textContent = ''; matchesOutput.innerHTML = ''; if (!pattern || !text) return; try { const re = new RegExp(pattern, flags); const global = flags.includes('g'); if (global) { let match; let results = []; let count = 0; while ((match = re.exec(text)) !== null && count < 1000) { const start = match.index; const end = start + match[0].length; let groups = []; for (let i = 1; i < match.length; i++) { if (match[i] !== undefined) groups.push(` Group ${i}: "${match[i]}"`); } results.push(`#${results.length + 1}: "${match[0]}" at [${start}-${end}]${groups.join('')}`); if (!re.global) break; count++; } if (results.length === 0) { matchesOutput.textContent = 'No matches found.'; } else { matchesOutput.textContent = results.join('\n'); } // Highlight matches in input if (results.length > 0 && results.length < 100) { let html = ''; let lastIdx = 0; re.lastIndex = 0; let m; while ((m = re.exec(text)) !== null) { html += escapeHtml(text.slice(lastIdx, m.index)); html += '' + escapeHtml(m[0]) + ''; lastIdx = re.lastIndex; if (!re.global) break; } html += escapeHtml(text.slice(lastIdx)); document.getElementById('regex-highlight').innerHTML = html; } else { document.getElementById('regex-highlight').textContent = text; } } else { const match = text.match(re); if (match) { let result = `Match: "${match[0]}" at [${match.index}-${match.index + match[0].length}]\n`; for (let i = 1; i < match.length; i++) { result += `Group ${i}: "${match[i]}"\n`; } matchesOutput.textContent = result; let html = escapeHtml(text.slice(0, match.index)); html += '' + escapeHtml(match[0]) + ''; html += escapeHtml(text.slice(match.index + match[0].length)); document.getElementById('regex-highlight').innerHTML = html; } else { matchesOutput.textContent = 'No match.'; document.getElementById('regex-highlight').textContent = text; } } // Mark test if (re.test(text)) { document.getElementById('regex-test-result').innerHTML = '✔ Test passed'; } else { document.getElementById('regex-test-result').innerHTML = '✘ Test failed'; } } catch(e) { errorOutput.textContent = e.message; document.getElementById('regex-highlight').textContent = text; document.getElementById('regex-test-result').innerHTML = ''; } } function escapeHtml(s) { return s.replace(/&/g, '&').replace(//g, '>'); } [patternInput, flagsInput, testInput].forEach(el => el.addEventListener('input', testRegex)); function showToast(msg) { const toast = document.getElementById('toast'); const toastMsg = document.getElementById('toast-message'); toastMsg.textContent = msg; toast.classList.add('show'); setTimeout(() => toast.classList.remove('show'), 2000); }