Does changing window.location stop execution of javascript?

Question

When writing server-side code you need to explicitly stop execution after sending a "Location: ..." header to the client or your code will continue to execute in the background.

But what about when you change window.location in a client-side script? Does this immediately stop execution of the current script or is it up to the programmer to make sure that any code located after this call is not reached?

@stolsvik almost anything, including it is useful, shows research effort, and is clear. Maybe it is also just worth reading, funny, intriguing, etc? — Andrew
– Andrew, Commented Aug 19, 2015 at 1:54
I had to explicitly call return; on the next line to get out of the flow and let window.location do its thing. — VPaul
– VPaul, Commented Apr 1, 2020 at 16:47

bobince · Accepted Answer · 2010-03-29 09:43:53Z

23

Does this immediately stop execution of the current script

No, the remaining handler script will execute to the end before control returns to the browser and events start happening. When loading of the new page gets far enough for ‘navigation’ to occur, the beforeunload and unload events will fire, then the page and any script in it will become inactive.

However, any further queued events and timeouts might not fire. For example if you navigate the page in a click handler of a form submit button and don't cancel the default action, it is possible (race condition) for the navigation to occur before the submit event queued by the default action of the click.

answered Mar 29, 2010 at 9:43

bobince

538k111 gold badges675 silver badges846 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

speedplane Over a year ago

Thanks. As a corollary to this question, is there any way to detect when you're in this state (i.e., window.location has changed but navigation has not yet occurred)?

Tomasz P. Szynalski Over a year ago

Thanks, just the answer I needed. Is your answer based on observing how browsers work, or is this behavior defined somewhere?

bobince Over a year ago

The answer was based on observation, but some work has been done in HTML5 on standardising browser control flow—asee eg w3.org/TR/html5/webappapis.html#event-loops, w3.org/TR/html5/browsers.html#navigate. The standards we have ended up with are largely unreadable, and still leave a bunch of stuff unspecified, but we're still in a better situation than the inconsistent and mysterious one we had before.

Jimmy · Accepted Answer · 2010-03-29 09:14:41Z

15

Setting window.location does not implicitly stop JS execution. Take the following as an example:

function locationTest() {
  window.location = 'http://www.google.com/';
  window.open('http://www.yahoo.com/');
}

locationTest();

Try running that from Firebug/Web Inspector/etc. and you'll notice that the current window will load Google, but a new window will open with Yahoo as well.

answered Mar 29, 2010 at 9:14

Jimmy

37.5k13 gold badges85 silver badges100 bronze badges

2 Comments

codymanix Over a year ago

This could be a race condition. I can imagine that old scripts stop executing when the new location has completed loading

Muhammad Faisal Iqbal Over a year ago

On Safari it seems that it stop execution after window.location

Collectives™ on Stack Overflow

Does changing window.location stop execution of javascript?

2 Answers 2

3 Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related