👀 Views: 37 💬 Answers: 1 📅 Created: 2025-06-09

regex node.js logging JavaScript

I'm updating my dependencies and I've been struggling with this for a few days now and could really use some help. I'm having trouble crafting a regex pattern to match custom log formats in my Node.js application. The logs can have varying structures, and I need to accommodate optional components. For example, a log entry might look like this: ``` 2023-10-15 14:32:10 [INFO] User 'john_doe' logged in from IP 192.168.1.1 ``` However, not all log entries contain the IP address or even a username. Some might just look like: ``` 2023-10-15 14:32:10 [behavior] System failure ``` I need a regex pattern that can capture the timestamp, log level, and optionally the username and IP address. I've tried the following regex pattern: ```javascript const logPattern = /^(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}) \[(\w+)\](?: User '(\w+)'( from IP (\d{1,3}(?:\.\d{1,3}){3})?)?)?$/; ``` When I test this pattern, I find that it sometimes fails to match logs without the username or IP address, returning `null`. Specifically, logs of the type `2023-10-15 14:32:10 [INFO] User 'john_doe' logged in` seem to work, but when the username is absent, I'm not getting the expected capture groups. I also tried modifying the regex to make the entire username and IP section optional, but then it ends up over-capturing or missing necessary fields entirely. Could anyone provide insight into how I can refine my regex for better matching? I'm using Node.js v16.13.0 and the `RegExp` class directly for parsing. Thank you! Am I missing something obvious? I'm working in a Windows 10 environment. How would you solve this?