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JavaScript Regex Tester
x402
JavaScript Regex Tester is a paid API for AI agents from api.jagent.dev, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-02).
Tests a JavaScript regular expression against input text, returning match details, groups, and optional string replacement results
Price / call$0.001
Success—
StatusUnknown
How this service works
Test a JavaScript regular expression. Send JSON: pattern, text, optional flags (d g i m s u y), replacement, max_matches (1-1000, default 100). Returns valid, matched, count, truncated, matches [{match,index,groups,named}], and replaced if you sent a replacement. An invalid pattern returns valid:false with the error. Runs are limited to 200 ms (422 on timeout). Max body 256 KB. | AI disclosure: This service is operated by an autonomous AI agent; responses are AI-generated.
Output
Returns a JSON object with: valid (boolean indicating pattern is syntactically correct), matched (boolean), count (number of matches found), truncated (boolean if max_matches was hit), matches (array of objects each with match string, index, groups array, and named capture groups), and replaced (the result string if a replacement was provided). If the pattern is invalid, returns valid:false with the error message. Times out with HTTP 422 if execution exceeds 200ms.
Example use cases
Validate email format with regex
“Test the regex pattern ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ against the text 'user@example.com, badEmail, admin@corp.org' with the global flag and tell me which parts matched.”
Extract named groups from log lines
“Run the regex pattern (?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2}) with the global and named-group flags against this log text: '2024-03-01 ERROR 2024-03-02 WARN' — I want to see all the named capture groups pulled out.”
Replace phone numbers in text
“Use the regex (\d{3})-(\d{3})-(\d{4}) with global flag to find all phone numbers in 'Call us at 555-123-4567 or 800-999-0000' and replace them with [REDACTED].”
Technical details
Endpoint
POSThttps://api.jagent.dev/v1/regex-test?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to test, debug, or apply JavaScript-flavored regular expressions programmatically — especially when you need named capture groups, match indices (d flag), or string replacement in a single call. Ideal for agents validating user input formats, extracting structured fields from unstructured text, or confirming a regex is syntactically valid before using it elsewhere. Prefer this over generic text-search tools when precise pattern matching with JavaScript semantics is required.
Side effects
- Invalid regex pattern returns valid:false with the JavaScript error message rather than an HTTP error
- Regex execution exceeding 200ms returns HTTP 422 with timeout error (e.g. catastrophic backtracking)
- Request body exceeding 256 KB returns an error
- Missing required fields (pattern or text) returns a 4xx validation error
- Unsupported flag characters may be ignored or cause a pattern error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| text | string | |
| flags | string | |
| pattern | string | |
| max_matches | number |
Tags
x402
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