Parsing a Custom Log Format in Node.js - Handling Variable Field Lengths and Missing Data
I've been banging my head against this for hours. I'm currently working on a Node.js application that requires parsing a custom log format. The logs are structured as follows: ``` 2023-10-01 12:00:00 INFO User123 - Action: Login | Duration: 3ms 2023-10-01 12:01:00 WARN User456 - Action: Logout | Duration: 2ms 2023-10-01 12:02:00 behavior User789 - Action: Purchase | Duration: N/A ``` Each log entry contains a timestamp, log level, user identifier, action description, and a duration. The scenario Iām working with is that the duration field is sometimes missing or labeled as "N/A", which I need to handle gracefully while parsing. I started by using a regular expression to capture the necessary fields, but Iām running into trouble when the duration is not a valid number: ```javascript const logPattern = /^(\S+) (\S+) (\S+) - Action: (.*?) \| Duration: (\S+)$/; const logs = ` 2023-10-01 12:00:00 INFO User123 - Action: Login | Duration: 3ms 2023-10-01 12:01:00 WARN User456 - Action: Logout | Duration: 2ms 2023-10-01 12:02:00 behavior User789 - Action: Purchase | Duration: N/A `; logs.split('\n').forEach(log => { const match = log.match(logPattern); if (match) { console.log({ timestamp: match[1], level: match[2], user: match[3], action: match[4], duration: match[5] === 'N/A' ? null : parseInt(match[5]) }); } }); ``` The question arises when I run this code; for entries with "N/A" for the duration, I want to store it as `null`, but when I try to parse it, it throws an behavior when hitting the `parseInt` function. The behavior I see is: ``` TypeError: want to read properties of undefined (reading '5') ``` I seem to be missing some condition to handle cases where the regex does not match perfectly. I've tried adding console logs to understand each step, but it still results in the same behavior. How can I effectively manage the variable lengths of fields and the potential absence of data without breaking the parsing process? Any ideas what could be causing this? I'm coming from a different tech stack and learning Javascript. I'd be grateful for any help.