How to Debug Code You Didn’t Write (your AI did) AI-generated code looks great in the diff and breaks on the first edge case. Here’s how to debug JavaScript you didn’t write without reverse-engineering someone else’s bad assumptions.

Whatever autocomplete casino your team is using this week, the bug report still lands on your desk like you wrote it yourself.

Here's how to debug code you didn't write (and didn't break).

trackjs.com/blog/how-to-debug-code-you-didnt-write/

#JavaScript #debugging

Who Watches the Vibe Coder? AI is shipping JavaScript faster than humans can review it. And a lot of it is “looks fine to me” code that explodes in production. You can’t code review vibes, so you need production visibility.

Vibe coding ships fast. Then prod finds the one weird browser + slow network combo and your “looks fine” code catches fire.

You can’t code review vibes, you need production visibility.

trackjs.com/blog/who-wat...

#JavaScript #WebDev

How to fix `undefined is not an object (evaluating 'window.webkit.messageHandlers')` Safari throws this when JavaScript tries to call the WKWebView native bridge, but the page is running in a normal browser context where `window.webkit.messageHandlers` doesn't exist. Fix it with featu...

Safari throwing “undefined is not an object (evaluating 'window.webkit.messageHandlers')”?

It’s not random. It’s WKWebView doing WKWebView things.

What it means, why it happens, and how to fix it:
trackjs.com/javascript-e...

#javascript #safari

How to fix `Unexpected end of input` JavaScript parser error when code or JSON data is incomplete. Often caused by missing brackets, empty API responses, or truncated scripts. Quick fixes: check for unclosed braces, validate JSON before ...

Unexpected end of input errors in production? Your code is fine. The server returned nothing when your JSON parser expected data. Empty responses, HTML error pages, truncated network calls.

trackjs.com/javascript-e...

#JavaScript #WebDev

How to fix `undefined has no properties` Firefox's error when destructuring null or undefined values. Common with API responses, missing function arguments, or async data not yet loaded. Quick fixes: add fallback objects, use default paramet...

Firefox throws "undefined has no properties" when you destructure null or undefined. It's the least helpful error message of all browsers for this problem.

What's happening and how to fix it: trackjs.com/javascript-e...

#JavaScript #Firefox

How to fix `Cannot destructure property 'x' of 'y' as it is undefined` Chrome error when destructuring properties from undefined objects. Common with API responses, function parameters, and React hooks. Quick fixes: add default values, use optional chaining, validate dat...

Destructuring fails loud. That's actually good.

Unlike dot notation that silently returns undefined, destructuring throws immediately when data is missing. Catches bugs faster.

trackjs.com/javascript-e...

#javascript #webdev

How to fix `Right side of assignment cannot be destructured` Safari's error message when destructuring null or undefined values. Common with API responses, missing function arguments, or async data not yet loaded. Quick fixes: add fallback objects, use optional...

"Right side of assignment cannot be destructured" is Safari's way of saying you tried to destructure null or undefined. Chrome tells you which property failed. Safari makes you guess.

trackjs.com/javascript-errors/right-side-of-assignment-cannot-be-destructured/

#javascript #webdev

How to fix 404 Errors from WebPageTest.org Bot 404 errors from WebPageTest.org bot checking for well-known configuration files like ads.txt, security.txt, and sellers.json. Appears in JavaScript error monitoring because WebPageTest uses real Chrom...

Seeing a sudden spike of 404 errors for ads.txt, security.txt, and /.well-known/ files? It's probably @httparchive.org Almanac scanning with WebPageTest

Not a bug, just bot noise.

trackjs.com/javascript-e...

#javascript #webdev

How to fix `Cannot read properties of null (reading 'length')` Common JavaScript error when accessing length on null values. Usually caused by DOM APIs like getElementById or querySelector returning null when elements don't exist, or localStorage returning null f...

"Cannot read properties of null (reading 'length')" is everywhere. That null tells you something: an API returned "not found." Here's how to track it down and fix it.

trackjs.com/javascript-errors/cannot-read-properties-of-null-reading-length/

#javascript #webdev

How to fix `Invalid or unexpected token` JavaScript parser error when it encounters unrecognizable characters. Usually caused by invisible Unicode characters, smart quotes from copy-paste, or BOM markers. Different from "Unexpected token X" ...

The worst JavaScript errors are the ones you can't see.

"Invalid or unexpected token" usually means invisible characters snuck into your code. Smart quotes from Slack, zero-width spaces, BOM markers.

trackjs.com/javascript-e...

#javascript #webdev

How to fix "The string did not match the expected pattern." Safari's generic error when DOM APIs receive invalid string arguments. Triggers include invalid CSS selectors, JSON parsing failures, contentEditable with bad values, and Performance.measure() issues....

Safari's "string did not match the expected pattern" is infuriating. One vague message for five different problems. CSS selectors, JSON parsing, DOM values, all the same unhelpful text.

trackjs.com/javascript-e...

#JavaScript #Safari

Installing TrackJS on CertKit YouTube video by TrackJS

Most JavaScript errors in your monitoring dashboard are garbage. Browser extensions, ad blockers, crawlers. Here's how I set up TrackJS to ignore the noise and only alert on real bugs that matter.

www.youtube.com/watch?v=HBaZ...

#javascript #errormonitoring

How to fix `The operation is insecure` Browser security error when JavaScript attempts restricted operations in non-secure contexts. Common with localStorage in iframes, geolocation on HTTP, or cross-origin operations. Quick fixes: use HTT...

Your JavaScript tried to use localStorage in a sandboxed iframe and now the browser is yelling at you.

"The operation is insecure" is rarely a real bug, it's just browsers being paranoid about security contexts.

trackjs.com/javascript-errors/the-operation-is-insecure/

#JavaScript #WebDev

How to fix `Failed to fetch: Facebook Privacy Sandbox` Network error when Facebook's Topics API registration fails. Common with ad blockers and privacy extensions. Topics is Facebook's implementation of Privacy Sandbox interest-based advertising. No user ...

Your monitoring dashboard flooded with Facebook Privacy Sandbox errors? They're not bugs. They're privacy tools doing their job. Stop wasting time fixing user privacy choices.

trackjs.com/javascript-e...

#JavaScript #WebDev

How to fix `Failed to connect to MetaMask` Browser extension error from visitors using MetaMask cryptocurrency wallet. Extension attempts to inject Web3 functionality into all pages, causing errors unrelated to your site. Safe to ignore via er...

MetaMask throwing connection errors in your logs? You're not alone. These extension errors pollute your monitoring with noise that isn't even your fault. We show you how to filter them out automatically.

Read more: trackjs.com/javascript-e...

#JavaScript #WebDev

How to fix `$ is not defined` Common JavaScript error when jQuery code runs before the library loads. Usually caused by script ordering issues, CDN failures, or async loading problems. Quick fixes: check script order, add fallback...

$ is not defined.
I have seen this error so many times. Here's how to fix it.

trackjs.com/javascript-e...

CA Alternative Launches Free Beta for 47-Day Certificate Lifetime Reduction Platform enables Let's Encrypt free certificates at scale, replacing expensive enterprise tools and error-prone scripts ahead of certificate lifespan reductions

I have no idea if this works, but I did my very first Press Release today!

I'm not really sure what to expect with it -- probably nothing lol. But I think we're doing something really interesting with @certkit.io .

www.einpresswire.com/article/8583...

How to fix `Unexpected token '<'` This SyntaxError happens when code tries to parse HTML as JSON. Usually your API returned an HTML error page (like a 503 gateway error) instead of the JSON data you expected. Here's how to handle it p...

I wrote up a debug log on one of my "favorite" errors of all time: Unexpected Token: '<'

It's currently the #15 most common error on the Internet.
trackjs.com/javascript-e...

#javascript #webdev #debugging

The design process of the TrackJS redesign #coding #programming #webdesign #debugging #css YouTube video by TrackJS

Eric from TrackJS talks through the design process of the 2025 reskin project.

youtube.com/shorts/UVk5g...

We finally got rid of Bootstrap css! #coding #programming #webdesign #debugging #css YouTube video by TrackJS

Jordan celebrates finally getting rid of bootstrap styles in the TrackJS redesign.

youtube.com/shorts/2vkdD...

Learn more about the TrackJS redesign 👇
trackjs.com/blog/a-fresh...

That moment when your Lighthouse score is 💯 but users are still complaining about slow pages...

Stop guessing, start measuring what they actually experience.

requestmetrics.com/web-performance/you-need...
#WebDev #Performance

Building a "Dark Mode" for the UI #coding #programming #webdesign #debugging YouTube video by TrackJS

Eric from TrackJS talks about the most-requested feature from the redesign project: Dark Mode.

youtube.com/shorts/NT2Am...

Learn more about our redesign 👇
trackjs.com/blog/a-fresh...
#video #code #javascript #design

Lowering the barrier to user feedback #coding #programming #webdesign #debugging YouTube video by TrackJS

Jordan Griffin discusses lowering the barrier to getting user feedback during the redesign of ⁨TrackJS⁩ .

youtube.com/shorts/e4URn...

Learn more about the TrackJS redesign 👇
trackjs.com/blog/a-fresh...

Cleaning up your old code #coding #programming #webdesign #debugging YouTube video by TrackJS

We recently launched a totally redesigned UI for TrackJS. Here's our CTO Eric talking about what we learned from it.

www.youtube.com/shorts/Je8TN...

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