Stuck on an issue?

Lightrun Answers was designed to reduce the constant googling that comes with debugging 3rd party libraries. It collects links to all the places you might be looking at while hunting down a tough bug.

And, if you’re still stuck at the end, we’re happy to hop on a call to see how we can help out.

meta-viewport: Cannot read property 'toLowerCase' of undefined

See original GitHub issue

We’ve been getting a bunch of users hitting the same snag recently: https://github.com/GoogleChrome/lighthouse/issues/10908

It now looks like it’s all due to the meta-viewport rule. It’s marked as incomplete and has an .error.message of Cannot read property 'toLowerCase' of undefined.

We’re using axe 3.5.3 and briefly looking at the changelog I have a suspicion our culprit is #2137 (“fix(meta-viewport): parse negative and string values for maximum-scale”)… which does include a few calls to toLowerCase().

@widmanski’s comment has a conjecture that looks compelling to me:

Update I’m pretty sure the error resulted from axe-core failing to parse our viewport tag due to legacy / invalid content (we copied it over from the previous version of the website) - <meta name="viewport" content="width=device-width,initial-scale=1,minimal-ui"> - minimal-ui is likely what causes this. We’ll be removing it soon, so lighthouse may actually start to correctly score accessibility on the reported page once you read this.

Edit: fwiw in Lighthouse we’ve been using https://github.com/dontcallmedom/metaviewport-parser for a while. Weight-wise it’s certainly heavier than your implementation, but it’s quite careful and thorough.

Issue Analytics

State:
Created 3 years ago
Comments:7 (5 by maintainers)

Top GitHub Comments

1reaction

strakercommented, Jun 5, 2020

It should make it into the 4.0 release.

1reaction

strakercommented, Jun 5, 2020

@bhavin7181 we are currently working on a fix for that bug. It might be related to #2261 or #2262.

Top Results From Across the Web

Cannot read property 'toLowerCase' of undefined postcss

I was using angular metronic. I got the same error and after a long time I found the wrong code block and commented...

Cannot read property 'toLowerCase' of undefined

hello i am try to check seo in my post data butits not open tabs after check in console it have error on...

cannot read properties of null (reading 'controls') - You.com

The cannot read property of null error occurs in JavaScript by: Calling a “click ()” function on a “null” value i.e DOM element...

iOS: Cannot read property 'toLowerCase' of undefined - ionic-v3

So I tried to test it with my real phone and it worked as well. But now I'm getting this error: Reading build...

axe-core/axe.js - chromium/src/third_party - Git at Google

utils.forEach(requestHeaders, function setRequestHeader(val, key) {. if (typeof requestData === 'undefined' && key.toLowerCase() === 'content-type') {.