Tamás Pap Tamás Pap - 4 months ago 86
Javascript Question

window.onpopstate on page load

I'm playing with

window.onpopstate
, and there is a thing that annoys me a little bit:


Browsers tend to handle the popstate event differently on page load.
Chrome and Safari always emit a popstate event on page load, but
Firefox doesn't.


source

I tested it, and yeah, in Chrome and Safari 5.1+ the popstate event is fired on page load, but not in Firefox or IE10.

The problem is, that I want to listen only to
popstate
events where user clicked the back or forward button (or the history was changed via javascript), but don't want to do anything on pageload.

By other words I want to differentiate the
popstate
event from page load from the other
popstate
events.

This is what I tried so far (I'm using jQuery):

$(function() {
console.log('document ready');

setTimeout(function() {
window.onpopstate = function(event) {
// Do something here
}, 10);
});


Basically I try to bind my
listener
function to
popstate
late enough to be not bound on page load, only later.

This seems to work, however, I don't like this solution. I mean, how can I be sure that the timeout chosen for setTimeout is big enough, but not too big (because I don't want it to wait too much).

I hope there is a smarter solution!

Answer

Check for boolean truth of event.state in popstate event handler:

window.addEventListener('popstate', function(event) {
    if (event.state) {
        alert('!');
    }
}, false);

To ensure this will work, always specify a non-null state argument when calling history.pushState() or history.replaceState(). Also, consider using a wrapper library that provides consistent behavior across browsers.