Trigger focus on input on iPhone programmatically

It seems that Safari mobile on iPhone does not allow one to programmatically set the focus to an input element if this does not come from a user interaction.

This means that if you listen to some event to set focus to an input, the focus won't be set on Safari. This also means that if you create a new call trace by wrapping your call in a setTimeout, you're also out of luck.

HTML only attempt

I was using the HTML default behavior of labels being bound to their inputs through the for and id attributes to automatically hide/display part of my UI when a specific label was clicked. This in turns checked/unchecked an hidden checkbox that I was using in a CSS selector selector.

Something like:

.my-ui { 
  display:none;
}
.my-checkbox:checked + .my-ui {
  display: block;
}

Adding a bit of JavaScript

And then, I was listening to the change event on my checkbox to trigger a focus event on an input in my UI.

This worked quite well on desktop but fails on iPhone. After some Googling, it turns out that Safari has a mechanism to protect auto focus of inputs. Inputs can only be programmatically focused if the order comes from a user interaction.

This means that if you call .focus() in a click handler, this is ok, but this won't be ok if called from a change event or a setTimeout.

Replicating standard behavior

In my case, I had to bypass the whole standard label behavior and rewrite it in JavaScript to be able to trigger my focus event. Here is what I did:

$label.on('click', function(e) {
  $checkbox.click();
  e.preventDefault();
  $input.focus();
});

This is actually me listening to the click event on the label, triggering a click on the checkbox (which will toggle the checkbox value) and disabling the default behavior (using e.preventDefault()).

Then I'm doing my input focus, which will work because it originated from a user interaction.

Conclusion

It's a shame that I had to disable common HTML behavior to re-implement it in JS, just so I can work around a weird bug in a specific proprietary implementation. But such is the life a web developer.


Tags : #javascript-iphone-focus

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