Webpage freezes in Safari on both iOS and OSX when the page reloads?

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I'm using an iPhone 11 Pro with iOS 15.3.1.

I'm trying to figure out why when visiting my website, Safari is freezing most of the time when the page loads. Sometimes the page loads the first time I visit it, but on reload it basically freezes with no interaction.

When I connect the iPhone to a Mac and use the Safari inspector to connect to the webpage on the iPhone, the inspector is basically blank on all screens. If I go to the "Elements" tab, nothing shows. If I go to the "Console" tab and try to execute some Javascript, nothing happens when I press enter.

On OSX, I can see similar behavior, except I can actually open the inspector before I visit the page. In this case, when it freezes I can see a few elements in the "Elements" tab, but that's about it. Any sort of interaction I try to do in the inspector results in nothing happening.

I'm at kind of a loss. How can the development experience for such a popular OS/Browser be so terrible, and how do I work around the inspector itself not working? I can't replicate this freezing on anything besides Safari.

To be absolutely clear on my question:

What is your process to debug a webpage in Safari when it is in a state where the inspector no longer interacts with the webpage?

safari freeze javascript ios
1 Answers

I did a broad divide and conquer of my app, commenting out top level code and working my way down uncommenting until I found the exact line that causes the freeze.

It seems calling HTMLInputElement.setSelectionRange() inside an onfocus event handler function caused an infinite synchronous loop in Safari, perhaps Safari synchronously blurs the input and refocuses for some reason when that function is called. And on page reload Safari was trying to focus on an input with that code automatically. That is my guess at least, removing the setSelectionRange() resolves the freezing problem.

Luckily, the freezing was fairly consistent so the divide and conquer approach worked. Unluckily, the inspector really should have done its job and picked up on the fact that the page was hanging and told me which function code execution broke at when Javascript was forced to stop, like Chrome or Firefox would.

If anyone has any better ideas for debugging these kinds of issues in Safari besides the programming equivalent of a short circuit test, I'll gladly accept the answer.

user_18174670
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