4 ms·

I posted it on the page as well: Doesn't just calling return from an event equate to returning boolean false, which means you are invoking the effects of preve

I posted it on the page as well: Doesn't just calling return from an event equate to returning boolean false, which means you are invoking the effects of preventDefault() and stopImmediatePropagation() thus explaining why with return it's faster as the event stops bubbling immediately?

EmielMols 13y ago
No. It equates to returning undefined, which is the same as having no return statement at all.
- dreen 13y ago
  Although it obviously isn't quite the same. I wonder what is the test result for no return vs return true
  - Tarang 13y ago
    Still faster, check revision 6 http://jsperf.com/always-return-on-jquery-events/6 http://jsperf.com/always-return-on-jquery-events/6 revision 7 http://jsperf.com/always-return-on-jquery-events/7 http://jsperf.com/always-return-on-jquery-events/7. Just return vs return true (faster). But as smilekzs points out revision 3 this might not be about the return statement.
- lucideer 13y ago
  !!undefined === false
  - bengillies 13y ago
    right. undefined is falsy, but it's quite different to false (i.e. undefined !== false)
    - lucideer 13y ago
      true, but a boolean return value is expected for event listener callbacks.
      - Stratoscope 13y ago
        That's not quite how it works. jQuery checks specifically for false with an === comparison. It doesn't do anything like a !! on the return value to convert it to boolean true or false. It only calls stopPropagation and preventDefault when the return value is false, not just any falsy value. I posted the jQuery code in a previous comment; take a look at that and you can see how it works.
al2o3cr 13y ago
FWIW, the underlying jQuery code explicitly tests for false with ===: https://github.com/jquery/jquery/blob/a5037cb9e3851b171b49f6d717fb40e59aa344c2/src/event.js#L317 https://github.com/jquery/jquery/blob/a5037cb9e3851b171b49f6... So returning undefined does NOT stop propagation.

EmielMols 13y ago

No. It equates to returning undefined, which is the same as having no return statement at all.

dreen 13y ago
Although it obviously isn't quite the same. I wonder what is the test result for no return vs return true
- Tarang 13y ago
  Still faster, check revision 6 http://jsperf.com/always-return-on-jquery-events/6 http://jsperf.com/always-return-on-jquery-events/6 revision 7 http://jsperf.com/always-return-on-jquery-events/7 http://jsperf.com/always-return-on-jquery-events/7. Just return vs return true (faster). But as smilekzs points out revision 3 this might not be about the return statement.
lucideer 13y ago
!!undefined === false
- bengillies 13y ago
  right. undefined is falsy, but it's quite different to false (i.e. undefined !== false)
  - lucideer 13y ago
    true, but a boolean return value is expected for event listener callbacks.
    - Stratoscope 13y ago
      That's not quite how it works. jQuery checks specifically for false with an === comparison. It doesn't do anything like a !! on the return value to convert it to boolean true or false. It only calls stopPropagation and preventDefault when the return value is false, not just any falsy value. I posted the jQuery code in a previous comment; take a look at that and you can see how it works.

al2o3cr 13y ago

FWIW, the underlying jQuery code explicitly tests for false with ===: https://github.com/jquery/jquery/blob/a5037cb9e3851b171b49f6d717fb40e59aa344c2/src/event.js#L317 https://github.com/jquery/jquery/blob/a5037cb9e3851b171b49f6... So returning undefined does NOT stop propagation.